M14 Forum banner

Working on Rear Sight Assemblies

22K views 28 replies 9 participants last post by  sinestrum308 
#1 · (Edited)
Part I – Checking Rear Sight Assemblies

Folks, there is a good bit of “Ye Olde Art and Mysterie” about working on rear sights than many folks imagine and it is not an exact science nor a simple matter of replacing parts to get them right. What makes it even more difficult is that no commercial receiver is totally correct in the rear sight area. Even when you have a correctly milled rear sight area as on a REAL G.I. M14 or M1 Garand, there are still enough tolerance differences or tolerance stack up that can cause you problems. Also, there is no way a fix for one Rear Sight (RS) will automatically fix a problem with a RS on a different receiver.

The first thing I do when inspecting a real M14, M1 Garand or any commercial M14 rifle is to grab my pair of Brownell’s Magazine Tube/Cap Pliers. These have hard rubber like pads that will hold the pinion drum securely without damaging it. You could also wrap thin leather around the pinion drum and grab them with slip joint pliers. Then I use a screwdriver with a tip that matches the slot in the nut in the center of the pinion and try to tighten it. Usually, I find these nuts somewhat to very loose and that’s bad as they need to be tight. Sometimes all you have to do to fix a problem rear sight is to tighten this nut. I’ve also been informed the Brownell’s pliers were actually some kind of automotive pliers, but I’m not sure as I’m not an auto mechanic. Anyway, here’s a link showing these pliers.

http://www.brownells.com/.aspx/pid=13787/Product/MAGAZINE_TUBE_CAP_PLIERS

Once you know the nut in the pinion is tight, it is time to check the windage knob to see if you can turn the knob. If it is too tight or too loose, then the nut in the windage knob may not be tightened correctly. What I have found to be the “sweet spot” for most sights is that when you tighten this nut, the first time it JUMPS into position is most often the correct amount of tightness. I sometimes go one more half turn when the elevation pinion has a worn triangular projection or the spring tension in the pinion is worn. If that causes the windage knob to be too tight, then you need to back off the nut to the first setting. SPECIAL NOTE: I have used this extra click of tightness on windage knobs that make it a little difficult to turn the windage knob to save the person from having to buy a new pinion. If WHILE you push inwards on the nut in the elevation pinion and at the same time then can move the windage knob, that may save you from having to buy a new pinion for a while. It isn’t as convenient as just turning the windage knob, but it saves you rather big bucks on a new pinion.

The next thing I do is run the aperture up about 10 clicks to see the clicks are solid and consistent. Then I leave the aperture there. I use my thumb to press downwards and forwards on the aperture to see if the aperture will slip and slide downward. Now A CAUTION HERE: On even the most perfectly fitted and working RS assembly, if you use enough pressure, you CAN AND WILL force the aperture down. That is NOT a valid test. If the aperture slips with very little pressure, you can try tightening the windage knob one more half turn. If that doesn’t fix it, you may be able to fix the problem with a tighter fitting rear sight cover, but you may also need a new elevation pinion. If that extra half turn on the windage knob does fix it and if now you can not move the windage knob, again you may need either a different rear sight cover or a new elevation pinion. On NM RS apertures, I run the aperture up to 30 clicks and try it again as NM shooters will often use that much elevation.

The next check is to turn the windage knob 12 clicks to the right and back to zero than 12 clicks to the left and back to zero. (24 clicks each way with NM ½ minute windage knobs.) This ensures the RS base moves correctly and comes back correctly according to the hash marks on the receiver. If the windage knob is too hard to turn or skips or catches, then a different RS cover is often in order OR you have problems inside the receiver.

The next thing I check is to push in on the right and then the left side of the RS base. You want the RS base to either not move or spring back when you release tension. This was not considered absolutely necessary on a G.I. rifle, but it makes for a more consistent rear sight adjustments. If it does not pass this test, usually you need a different RS cover.

There are additional things we check on NM RS assemblies, though that can go to a full book length to explain and really is too involved for anyone but an Armorer or Gunsmith.
 
See less See more
#3 · (Edited)
Part II

Inspecting Rear Sight Parts

The first part to inspect is the elevation pinion. After tightening the nut, you want to look at the condition of the triangular projection on the inside of the drum. That engages the serrations on the left side of the receiver. If that triangular projection is rounded over or worn down a lot, you have to replace the pinion because it won’t give you good clicks of elevation. There are some people who are rewelding and recutting these projections, but the cost is now more than a replacement pinion.

You can't really tell by sight if the windage knob will work correctly unless it is obviously damaged. I’ve only run across a half dozen windage knobs that had the “C:” spring worn too much in over 35 years of working on these rifles.

On apertures the first thing to check is to see you have a good ROUND hole in it. If it is dinged or malformed, it is really better to replace it. Aperture sights work because the greatest amount of light coming through them is in the middle of the hole. If the hole is not round, that will throw your eye off even if you don’t realize it. I also prefer to use apertures that fit as tight as possible side to side and still move freely – even with standard G.I. sights. I measure the width of the apertures and the grooves in the RS base for them to ge the ones with the least amount of slop between these two parts. Now, they didn’t worry about that on G.I. M14’s or M1 Garands, so it is not absolutely necessary, it just makes the RS a little better. I know of no one who will sell you a different standard RS aperture by width, but if you go to Gun Shows and take a pair of dial calipers or micrometers, you may find a wider one than you now have.

You basically check the RS base for obvious damage or cracks. They are actually a very strong part and only very unusually do you find something wrong with them.

As to the RS cover, we have to remember it is a large spring. About the only thing you can look for is the condition of the indent that bears against the top of the RS aperture slide. You turn it upside down to check it. I prefer ones that are not gouged in the center of the “dimple” as that can cause problems when you move your windage knob side to side. You can’t look at them and tell if it will fit correctly, or if they are too tight or too loose. NOS RS covers CAN have too much tension for commercial M14 receivers due to the way those receivers are milled for the cover and base. That’s important to remember. I’ve seen NOS RS covers that froze up the RS assemblies HARD on commercial receivers. So it is best not to throw away a RS cover as many will fit correctly on some other rifle.
 
#4 ·
MGySgt Fisher,

Thank you for taking the time to share your expertise.

This series needs to be saved as a sticky for future reference, as it is something that needs to be checked on every rifle!
 
This post has been deleted
#6 ·
Part III

Some of you have read that I was the Instructor of OJT’s (On The Job Trainee’s or Apprentices) and later on the NCOIC of the NM Rifle (M14) Rebuild Section at the Rifle Team Equipment Repair Shop at Quantico, VA while on active duty. I didn’t come from a metal working background when I came to the RTE shop for my one year OJT program, so I had to sweat some blood to catch up or work things out. (For example: It was NOT pretty watching me figure out how to hand file metal flat. Grin. But, when I figured out how to do it, I could teach it to others so they would better understand.) That actually made me a better Instructor as I could understand the difficulties my OJT’s were having and it caused me to look for ways to do things in an orderly approach.

I mention this because instead of using a “shotgun” approach to working on rear sights where I give examples of “If this is wrong – try this, that or something else,” I believe it is far better to go through the whole RS in a systematic approach. That way you can identify and correct things as you go and you will better understand how everything is supposed to work. However, I’m also sorry to say that sometimes you have to go back and change something when further along in the process you find something wrong. IOW, don’t expect that changing one or more things will automatically give you a good to great RS. You have to use patience to work RS’s and sometimes you just have to have the stubbornness of a Mule and not give up to get them right.

SPECIAL NOTE: Over the last 35 plus years of working on commercial receivers, I have learned the HARD WAY that the very first thing to do on a new/bare commercial receiver is to try to fit the RS. If the RS area of the receiver is screwed up badly, then the receiver goes back to the factory as long as there is a warranty on the receiver. On a few commercial receivers over the years, I built the rest of the rifle first and did the RS as one of the last things like we did on REAL G.I. M14’s and M1’s. Well, a few commercial receivers were so bad there that I had to strip the receiver down and send it back – thereby wasting a lot of building time on those receivers. So by doing the RS first, you may avoid some serious problems.

Trust me, I’ve learned it saves time to go through the following procedures when working on commercial receivers and will go through these techniques when I have a problem with the RS on a REAL G.I. M14 or M1 Garand.

OK, the first thing is to either start with a bare receiver or take the whole RS assembly off the receiver. Orientation of the receiver for this whole procedure will be the front of the receiver pointing away from you and in the upright position, the same way it would be on a rifle when you fire it. To disassemble a RS, you first loosen the windage nut until it just spins and you can pull the elevation pinion out from the left side of the receiver. Then unscrew the windage knob until it comes free of the RS base and pull it out the right side. Then take a screwdriver and force it in place under the bottom rear of the RS base and between the RS base and receiver. Pry up on the screwdriver until the RS Base and RS cover pop out as a unit. Pull the aperture up and back it out of the rear sight base. Then the Base and cover will come apart in your hands.

I bought a ¾” wide, triangular, Medium India stone years ago to use for RS work. The reason I bought the triangular or “Three Square Stone” as it is also called, was it was cheaper than a square stone, not because the triangular shape is better. So if you find a square stone instead, that’s fine. What I do is lay the stone all the way up into the RS base area on the receiver. I keep it flat and go forward and back and side to side for a few strokes each way. I’m not trying to remove any metal. What I’m doing is to polish the surface the RS base moves over and to see how flat and even the surface is. This because the RS base is going to move side to side over this area and you want that surface to be pretty flat. Even on G.I. receivers, you will see milling marks there and that’s no problem. What we don’t want is high spots in the very front of the milled out area as that can/will cause the aperture to tighten up or freeze up too much and we don’t want the very rear of the milled out cut to be high as that could cause the RS base not to travel smoothly. Even on G.I. receivers, this surface will not be and doesn’t have to be perfectly flat and smooth.

Now, I can’t tell you how many times over the years I’ve seen problems with this surface on commercial receivers. I’ve seen high spots on the front and rear and high spots to the left or right sides. In worse case scenarios, I’ve had to use a stone or diamond file to flatten the high spots and get the surface more even. You can use the ¾” wide stone to level things up, but if it takes more than you can flatten with 20 or 30 strokes of a stone – it is time to return the receiver/rifle to the factory or take it to a real M1/M14 Armorer. I can not and do not recommend the average person use a diamond file to flatten this area as you can ruin a receiver.

The next step is to put JUST the elevation pinion and windage knob in place through the holes of the receiver “ears.” I’ve actually seen receivers over the years where the holes for these parts were too small or off angle. Usually such problems can be fixed by a knowledgeable Armorer or gunsmith enough where the RS will work correctly. Tighten the windage knob until the nut JUMPS in place as that is the sweet spot. What we are checking is the serviceability of your elevation pinion and windage knob. If you get good, noticeable and even audible clicks when you turn the elevation pinion, that’s what we want. If you don’t, then it’s time to look at the triangular projection of the elevation pinion and the receiver serrations. If the pinion and windage knob are good, you can NOT fix the receiver serrations. You may have an elevation pinion where the spring inside is worn too much and a substitute pinion will work. If that doesn’t work, then try a different windage knob. It those don’t work, that would cause you to send the receiver/rifle back to the factory OR you can use a set of WWII M1 Garand Lock Bar sights on the rifle. Over the years, I’ve seen about a dozen commercial receivers where you had to use Lock Bar sights to get a useable RS. That was the only choice when the factory warranty was only good for a year or no factory warranty for whatever reason. NOTE: There is no warranty on the Chinese receivers, so using a set of WWII Lock Bar sights may save your bacon with some of them.

OK, with the elevation pinion and windage knob working or replaced, it is time to go on to the next thing. This post has gone on long enough, so I will write more in the next post. Stay tuned.
 
#7 ·
OOps, a P.S. to my last post.

When the holes in the receiver for the elevation pinion and windage knob are too small or "cattywompous," you can usually fix them with a FINE sanding cartridge roll in a dremel tool used very carefully. What I do is put a layer of Dykem blue all around the holes and see where they are binding - by where the blue dye is worn off. A little polishing with the fine cartridge roll or a cratex point is done and you try and check and try and check until the holes are corrected.
 
This post has been deleted
#9 ·
In a shameless plug for my own product, I sell rebuild kits to replace hoods on a MN sight. If that little C clip comes unwound (usually during a match),
Art,

Got a chuckle out of that statement about a shameless plug. $15.00 for the whole kit is cheap insurance if you shoot any kind of matches with a hooded rear sight. I would recommend anyone who competes with them get one of these and put it in your shooting kit.

Why do I say that? Well, we could have used one at Camp Perry just last year. The comedy of errors began when a good buddy and Distinguished shooter friend of Mike Gingher and mine decided at the last minute to put NM sights on his M1A to compete. (Don't even get me started on the lack of wisdom about waiting till just before a match to change sights. Grin.) Anyway, I had one set each of fitted .595 and .520 NM apertures and RS bases. Mike and I suggested the .595 sights due to the our buddy's age. Well, they are out zeroing the rifle the morning before the match and guess what? Our buddy bumped the hood on something and it popped off. Now Mike and I have replaced many hoods on RS hooded apertures,but he didn't have a tool with him. I'm back in the Armalite Booth with the tools, but they really didn't have time to come back, get it fixed and go back out. So they installed the .520 aperture and hood. Well, it was a bit too small for our buddy's eyes and it would have been better had he or Mike had one of these kits to repair the .595 hood and get a good zero with it.

Oh, and Art is correct that sure as shootin when something goes wrong with a NM hooded aperture, it is almost always in a match or when you really need it. Murphy ensures that.
 
#8 ·
What am I hurting on my rifle???

I ask because what I've been doing (just once after sighting in at 25 yds) is counting the clicks to full bottom, loosening the screw in the elevation knob, setting the elevation knob so it lines up (yards wise for 250 for my BSZ) and then snugging up the screw while holding the knob and then using the screw driver to tighten up the screw after the knob turns around to the full up position.

Is this damaging the teeth on the sight or the pinion? Thanks.
 
#10 ·
No, you should not be damaging the pinion as long as you hold the drum of the elevation pinion with something that won't mar or crack it - while you loosen or tighten the screw. If your fingers are strong enough to hold the drum, then you are in tall cotton. Most folks' fingers aren't strong enough to hold the drum securely enough to do that, though.

BTW for the folks who don't know, this is basically how you use the engraved and numbered hash marks on the elevation pinion drum to get a basic zero on a rifle - as the pinion was designed. Then if you had to shoot at longer ranges, you were supposed to move the elevation pinion to the higher engraved and numbered hash marks. In reality and in the Marine Corps, we didn't use the hash marks on the elevation drum. We kept track of how many clicks of elevation were used for each yard line. In combat, we set the sights at a BZO of 300 yards and just held high for longer ranges.
 
#11 · (Edited by Moderator)
pliers

gus:
those pliers are an esstential item for most aircraft mechanics.
they are for cannon plugs found on airframes engines and avionics and instruments.
technical name as per aviation types as well as dod types are pliers soft jaw cannon plug.
you can get them cheaper on ebay or right from any aircraft tool supplier.
gus you are a most knowledgeable guy and your posts are spot on. regards jeff shapiro hueygunner
 
  • Like
Reactions: Deacon
#15 ·
gus:
those pliers are an esstential item for most aircraft mechanics.
they are for cannon plugs found on airframes engines and avionics and instruments.
technical name as per aviation types as well as dod types are pliers soft jaw cannon plug.
you can get them cheaper on ebay or right from any aircraft tool supplier.
gus you are a most knowledgeable guy and your posts are spot on. regards jeff shapiro hueygunner
Jeff,

That's great info and should be of good use to many folks. Thank you.
 
#17 ·
Part IV

The next thing to go over is the RS Base (hereafter referred to as the Base for brevity.) On many of both the standard and NM bases, the very front bottom edge of the base sometimes has a burr or slight downsweep on them from the manufacturing process. On some of the NM bases, the pad on the front bottom edge of the base was made a little too far down. On some NM bases, the bottom rear edge also sticks down a bit low. So I’ve come to take my ¾” stone and slide it sideways on the entire bottom of most bases I work on to get rid of burrs and see if there is such a high spot on the front bottom pad. A few strokes sideways, like one is draw filing, is all you need to do at this time to ensure there are no burrs. NOTE: The ENTIRE bottom of surface of the base is NOT entirely flat, though, as the rear of the base sticks down farther than the front. The main purpose of the Base sticking down in back is to ensure the rear sight cover won’t be popped out and as a dust shield – as far as anything I’ve ever been able to determine.. The base is meant to slide and be supported on the large machined flat portion of the receiver. Then you take the elevation pinion and windage knob off the receiver to go on to the next step.

Now you want to mount JUST the elevation pinion, RS base and windage knob. We are doing this to isolate any problems the RS base might have and fix them now, as much as possible. Tighten the nut on the windage knob to the “sweet spot” mentioned before and then turn the windage knob to center the RS base on the center engraved hash mark line on the receiver scale. Now it’s time to turn the windage knob so the Base goes ALL the way to the left. What we are looking for is if the scribed lines give us a good reading and if there are any bumps, catches or stops that slow down or stop the Base from moving to the left. The longer scribed lines on the receiver scale are supposed to represent 4 clicks of windage on a standard RS and 8 clicks on a ½ minute NM RS Base. What we are really looking for is to see if there is enough clearance for the Base to move freely.

If the holes for the windage knob and elevation pinion were drilled down too far close to the surface of metal the Base rides on, that will cause hard turning of the windage knob or it will freeze up the Base when using windage adjustments. If that is going on with a Standard G.I. type Base, it is time to stop there. You either need a skilled armorer to look at it to see if it can be freed up or if it has to be sent back to the factory. Send it back to the factory if you don’t have someone experienced with working on Garands or M14’s to assist you.

If you feel some extra bumps, catches, etc. – what may also be happening on a commercial receiver is the flat shelf behind the rear sight ears of the receiver may not have been machined correctly. I’ve seen some pretty large burrs or insufficient machining back there. You can flatten that out with your ¾” stone and smooth it up as required. That shelf is basically just a clearance cut as the base rides on the machined surface above and in front of that shelf. So we are not concerned if you go a bit too deep clearing that shelf. BTW, if the holes for the pinion and windage knob were drilled too low on the receiver, the rear bottom of the Base will also bind up there.

If the machined surface for the Base is higher towards the left side of the machined cut on the receiver, that will cause the Base to begin to bind as you move the base towards the left. I’ve had to use the ¾” stone to take one side or the other down a bit so the Base won’t bind as it gets close to one side of the receiver. I’ve even had to use a diamond file on a very few receivers. If that is causing the binding, then it is time to get an experienced Armorer to look at it or send it back to the factory.

The next thing to check is to be real careful to look at the Base when it gets close to the left receiver ear. You don’t want the Base to be rubbing on the top of the receiver ear. This was a real problem in the early 80’s on SAinc. receivers and some receivers of other manufacturers since then. I still run into this occasionally with commercial receivers. What you do is use a rotary stone or sanding cartridge roll to clear the top of the receiver so the Base will ride over it without touching. Black magic marker or Dykem blue on the receiver ear will show you if the Base is rubbing on it. Once it is clear, use sand paper for metal to smooth it up. NOTE: I’ve been asked about clearing the Base instead of the receiver as the Base is the cheaper part. In this case we want to work on the receiver so if you or someone else ever decides to put another Base or NM Base on it, it will fit correctly. It does not matter if you cut through the hardness on top of the receiver ears as there is no stress on them.

Once the Base moves freely all the way to the left, do the same things and move it all the way to the right. Also do any clearing or stoning as required.

It is very, VERY unusual that the Base will bind or hang up on the very front bottom of the Base on that pad when you move it for windage at this point. That’s because there is no tension on the front part of the Base at this time. However, if the front bottom of the Base IS binding or hanging up and a few more strokes of the stone won’t clear it, then it is time to seek an experienced Armorer or send it back to the factory.

If the base has clearance and somewhat moves freely, but you notice something hinky or just not right about the way the base moves, I also suggest you try a different windage knob. What is possible, but is rather rare, is the C spring that gives tension to the nut in the windage knob may be wearing out. Trying a different windage knob should tell you if that is going on or not. This can also be caused by the spring in the pinion beginning to wear out.

At this point, you should be able to move the RS base all the way to the left and right side of the receiver without binding and so the engraved hash marks on the receiver scale align with the engraved line on the back of the Base. The scale on commercial receivers may be off a bit and we really can’t fix that. You will be keeping track of how many clicks of windage you use at every yard line anyway, won’t you? So that really isn’t a problem if the scale is not perfect.

We MAY have to work on the bottom of the RS base some more as we go along, so this is a case where we have to check and perhaps do more fitting on down the line.

Going to end this post and the next post or two will be on the Aperture.
 
#18 ·
Gus,

I love the detailed explanations, and was absolutely tickled by your observation that the aperture hole has to be round, or it will draw off your focus.

Without going into the optical math, I will say that I agree and disagree. Yes, if it is non-round, it will create a bias in your focus.
However, round is not the best shape.

I invented a rectangular aperture for the M-1A based exactly on the observation that for an opening of a certain size (ie constant brightness), if you ovalize the hole, it will bias your focus. If you make it wide horizontally and small vertically, it will improve focus on horizontal lines more, and diminish focus on vertical lines, and as long as you keep the total open area of the aperture constant, the brightness will not change.

As it turns out, for a front sight post, a round aperture is not the optimum shape, since your needs for horizontal focus and vertical focus are different. To judge elevation, you need great focus in order to put the top horizontal edge of the front post up against the bull. To judge windage, you are balancing the bull sideways between two vertical edges of the post. So if I can improve your focus on horizontal edges slightly by giving up some focus on vertical edges, this is a good trade.

Your brain has agreat ability to center things, so as long as your front sight has two edges, your eye can center the bull side-side between them, it does not matter if the sides of the front post are sharp, or fuzzy. But for elevation, you don't have the ability to center, because you only have one top edge to the post - so you need sharp focus to judge precise alignment.

I know this is true, because when you get an older shooter whose eyes have gone, the typical symptom is that they string their shot groups out top to bottom. This is because even with blurry vision, they can still center the bull to judge windage, but with blurry vision they cannot judge elevation.

I'm not the first person to figure this out - Mother Nature beat me to it. Ground level hunters, who need to focus btween vertical edges to find prey, because they are surrounded by grass (which is mostly vertical edges), have evolved slit shaped pupils. Cats, snakes, and some others have evolved a non-round pupil to help them preferrentially focus in one direction.

Thus, by replacing the round aperture with a horizontally oriented rectangle, I improve focus for elevation, by giving up slightly on focus of vertical lines. WIth a front post, this trade represents a net gain by improving a critical parameter in exchange for giving up a less important one.

Instead of a .052 round, I offer a 0.030" tall x 0.075" wide (same area - same brightness), but instead of the focus of a 052 on your horizontal edge, you get the focus of a 030 aperture on that horizontal edge.

I also make a 036 x 080, which lets in the same amount of light as a 0595 round.

Testing using ARs suggested there was an average 15% reduction in group size by using a rectangular aperture.

Art
 
#19 ·
Gus,

I love the detailed explanations, and was absolutely tickled by your observation that the aperture hole has to be round, or it will draw off your focus.

Without going into the optical math, I will say that I agree and disagree. Yes, if it is non-round, it will create a bias in your focus.
However, round is not the best shape.Art
Art,

You have done some remarkable brainstorming on using rectangular apertures. This is yet another example of how we all can learn something new. Is there a size rectangular aperture that you recommend as "better or best" for someone over 40, over 50, etc.? Also, do you know how astigmatism affects the use of the rectangular aperture? This has always been my personal problem and is the reason I was never able to be a Match Shooter.

But back to the general subject at hand on standard G.I. type apertures..... What I'm trying to get across to people is that if the standard G.I. aperture is dinged up or out of round, it will cause them problems in shooting as accurately as they would with a nice round, clean hole in the aperture. So if they want to keep to the original G.I. design of the rear sight, they should replace one that does not have a dinged up hole. They could also use a hooded rectangular hooded aperture, to be sure, but let's get rid of the apertures that have dinged up holes. Grin.
 
#20 ·
Gus,

Your questions are right on it.

1. There are limits to how rectangular you can go. In width, you never want the aperture to be wider than your pupil, otherwise it is you pupil that sets the depth of field, not the aperture, and since the pupil varies with brightness, your focus will be all over the place. Furthermore, if you are close to the same size, you get the risk of parallax error. If your head is slightly out of line, the image that enters your eye is bounded on one side by the pupil, and on the other by the aperture, which will cause things to appear to move sideways. Bottom line, around 0.080 to 0.100 is the maximum width, Pupils can get as small as 0.125", but that depends on lighting and the person in question.

2. For rectangular height, at some point you start seeing diffraction errors, als known as dust bunnies, or spider webs. Most people can see through a 0.025" slit without major issues, especially if the light is good. I have a few folks using 0.023, but that's minimum. Grab a pair of calipers, and hold them in front of your eye at the same distance as your rear sight (this is important) and open/close them slightly to see where you start seeing the image go dim, where you start seeing parallel lines. If I hold them close, I can get an image down to 0.020, but at rear sight distance it's more. Hold your finger out at arm's lenght, and use the calipers. If you hold the gap horizontal, I'll bet you see blur lines on the sides of your finger, and not on the top. Or just look at a roof line - if the calipers have the slot horizontal, all vertical lines you see will have much bigger blur than the horizontal lines you are looking at.

3. For astigmatism, these things work great! Instead of putting them horizontal, you align them to cross the axis of astigmatism in your eye. Basically, this is an adaptation of the slit that eye doctors used to use to diagnose astigmatism in people (at least before they invented laser scanners that just map the topography of your cornea). If you have astigmatism, your eye lens is shaped liek a football, instead of a basketball. As a result, objects that line up with different diameters of your lens all get slightly different focal treatment. A line from 4 oclock to 10 might be in great focus, but a line from 1 to 7 is miserable.

If I am going to design a slit shaped sight, that only lets a slice of image fall on your eye, why don't I align that slit so it falls on exactly the best slice of your eye?

Trust me, I can add 15 points to your score at 600, more in XTC, and put you in the game.

Art
 
#21 ·
Part V

Apertures

OK, I’m assuming you have an aperture with a good clean hole or have replaced it. Time to take the elevation pinion, windage knob and RS Base back off the receiver.

The “slide” or forward body section of the aperture should easily slide up and down in the base. If it doesn’t, then most likely there are burrs or dings on the slide or inside the groove in the Base. You can get rid of them with needle files. If there are no burrs and the aperture slide hangs up, then what most likely is going on is that someone tried to tighten the RS base by peening. This is something we commonly do on NM Apertures and Bases and you can usually see where someone peened in the sides of the base and/or where they annealed the base so the sides could be peened without cracking. (BTW, in this case peening means the piece was hit with a hammer to move metal in the direction you want it to go and that means closing up the space side to side for the aperture slide.) However, if the Base was peened and the slide doesn’t move freely, the job wasn’t done correctly. I may write something on tightening up NM hooded apertures towards the end of this article, but I’ll leave that subject for later right now. You may be able to free up a peened Base to fit the aperture slide by using lapping compound. The problem with that, though, is most people lap parts way too much before they stop. So for most people, I will suggest it is cheaper, easier and faster to just replace the RS base. If you have to do that, be sure to go back through Part IV to ensure the replacement Base fits correctly. Let’s go on assuming the aperture slide moves freely in the base.

Now it’s time to assembly JUST the elevation pinion, windage knob, aperture and base in the receiver and tightened to the sweet spot I’ve mentioned before. Turn the pinion so the aperture slide goes down and check you have good clicks while it goes down.

Where problems OFTEN arise with commercial receivers is the front bottom of the aperture slide catches, sticks or freezes when it close to being all the way down – maybe in the last one to three clicks before it reaches the bottom. This only happens once in a Blue Moon with G.I. M14 or M1 Garand receivers and I’ve only seen a problem less than 5 times with them in the last 35 years. The front bottom portion of the slide has a little over ¼” of smooth rounded area before the teeth begin and go on up towards the aperture hole. If the milling for the machined area of the receiver on which the RS base isn’t done correctly or completely, the slide might stick or catch on this front, smooth rounded area of the slide rubbing on the receiver. On regular G.I. sights, you just file or sand a little off this area until the slide works freely. You don’t want to sand the teeth, though, so it is best to wrap tape around them if you have to remove metal from the slide up front. You can also modify that front bottom area of the aperture slide like we do on NM apertures. Sometimes with commercial receivers you have to do that even with standard sights, but more on that later. OK, let’s assume the slide goes all the way down without catching or sticking.

Now it’s time to take a REAL close look at the top of the aperture slide when it is all the way down compared to the cut in the receiver for the RS cover. Run the RS base all the way to the left or right side to get a close look. The distance from that cut to the machined surface on the receiver may be too short. If the top of the aperture slide is below the cut for the cover, then you are good to go. If the top of the aperture slide is ABOVE the cut for the cover, the slide is going to jam and not go all the way down when the cover is in place. This doesn’t happen every time, but this does happen often enough with commercial receivers. Normally we can fix that by taking metal off the top front of the aperture slide. (BTW, this is VERY common with many of the cast NM hooded aperture slides as they tend to be a bit higher than G.I. aperture slides.) Because I’ve done so many of them, when I find an aperture is high, I go ahead and grab a rotary stone and start taking metal off the top of the aperture slide and then fine tune it later. For a newcomer, I’d suggest you wait until we get a little further along.

For the next step, we need to take the pinion, windage knob, base and aperture back off the receiver. (By the time you have done all these checks, your expertise at assembling and disassembling your RS should increase a lot. Grin.) Now grab JUST a RS cover and your aperture and base. Mount the aperture and base in the cover and put the front of the cover in the receiver groove and use a screwdriver blade to push forward and down just below the RS base on the cover until the cover snaps into place. Push the aperture low and then push forward on the base and release. We want to see if the base and aperture spring back when you release forward tension. MOST of the time, it is at or close to the ideal when the Base springs back quickly. If the base and aperture don’t spring back, it could be because the cover is not putting enough tension on the base and aperture. RS covers ARE springs and they can lose tension with age. Normally when this is the problem, it isn’t very hard to push the aperture and base forward. If that is the reason, you most likely will have to get a replacement RS cover. If the Base and Aperture DON’T spring back, one of two things is usually going on and they are: 1. The top front of the aperture or the bottom front of the aperture (or both) are binding up or 2. The RS cover is too tight for your receiver.

You have to rule out whether the aperture is binding first. Take the aperture, base and cover back off the receiver. Grab some Dykem Blue or a black magic marker and use it on the top front and top bottom of the aperture slide. Reassemble the parts on the receiver and push the aperture and base back towards the front, pull it back, push forward a few times then take the parts back off the receiver. You should see the Dykem or black worn off on either the top or the bottom (or both) if they are binding.

To clear up binding on the bottom front of the aperture, I normally clear them like we do for NM apertures. For a picture about how we modify the front bottom sections of NM apertures, go to : http://www.fulton-armory.com/, then click on the “M14 pages,” then click on the “M14 FAQ Articles,” then click on “National Match Rear Sights – What you need to know.” Go down the article until you come to “2. FITTING THE NM REAR SIGHT APERTURE” and you will see the basic way we file or grind metal off so the bottom front of the aperture won’t bind up on the receiver. OK, so how far back and up do you file on the aperture slide? Well, for REAL G.I. M14’s and M1 Garands, we always left the width of a tooth at the rear of the smooth rounded section when we filed this. That ensures the shooter can’t mistakenly add his 600 yard dope TWICE and run the aperture out of the base and fall on the ground while on the Firing Line. Some Armorers cut further back into the teeth area so the aperture CAN be run out of the base and the shooter can change aperture slides at different yard lines. I don’t recommend that practice and not many shooters actually do it because you can’t fit two apertures to a NM Base so they both are as tightly fitted. HOWEVER, on many commercial M14 receivers, I’ve found you HAVE to cut into or even cut out the first tooth at the bottom front of the aperture slide to stop it from binding on the receiver. What I recommend is begin by cutting no further back than the width of a tooth left on the smooth rounded section and then cut back more if you have to do so. You have to cut, mark with Dykem or magic marker, try, cut and try until it no longer binds up. If you also have to clear the top front of the Aperture, you will have to grind, mark, try and do that until it and the bottom front are cleared.

Now to clear the top front of the aperture, this gets a little involved. I’ve learned the first thing to do is round the top front edge of the aperture. Then mark the top front with Dykem or magic marker and try it again to see if and where it binds. I use a rotary stone in a dremel tool to do most cutting and then use a sanding cartridge roll to smooth out the top surface. By marking with Dykem or magic marker and keep trying the fit, the wear marks will show you the high spots you have to clear. You usually only have to work on the top front going back about ¼” to no more than about 3/8” to free up the top front of the aperture from binding. We are not worried about the RS cover applying much if any pressure at this point on the top of the aperture slide, but only clear/grind/sand as much as you need to stop it from actually binding.

While you are doing this, you also need to look and see if the bottom front of the aperture slide binds while you are clearing the top. If it is, continue to mark, file and clear it as well. What you need to wind up with is when the aperture is all the way down in the base and the cover is in place, the aperture does not bind up.

We aren’t done with this step, but I’m at a good stopping place and this post has gone on long enough. Stay tuned for more.
 
#22 ·
So why is it that when I secure the windage knob and tighten the screw, the screw still works loose during a course of fire??? Should I be using some loctite to secure it or is something wrong with my newist M1A??? I tightened this knob hard before a highpower match but 2 shots into my 600 yd stage I had to deal with a loose windage screw that worked itself loose with every attempt to retighten it. I would appreciate any and all constructive criticism or assistance, thanks much.
 
#24 ·
First, the screw in the elevation pinion may be loose and that is always the first thing I check. Refer back to the beginning of the thread on how to tighten the screw in the elevation piniion without marring or cracking the elevation drum.

Two things could be going on next. You could have an elevation pinion with a spring that has lost tension AND/OR you could have a loose nut in your windage knob - where the internal "C" spring is worn out. Please see Part VI I just posted above on a loose windage nut.
 
#23 ·
Part VI

Well, after referring someone to this thread, I see I stopped short, so had better go on.

The next problem you can run into is if the rifle shoots too high EVEN when the RS aperture is run all the way down and that can be caused by the RS aperture slide not going down far enough into the receiver clearance cut. In some cases, even a standard RS aperture will not go down far enough. The reason for this is on some commercial receivers, they didn't machine out the front of the clearance cut enough for the RS base and aperture. I have NEVER found this on an original M1 Garand or M14, but I have found this on a fairly good number of commercial M14 receivers. The check is to assemble the rear sight assembly BUT leave off the RS cover. Run the aperture all the way down and see if the front of the slide contacts the inside front of the receiver clearance. If it does, then look at where the aperture hole is located when the slide is all the way down. If the aperture hole is still above the receiver or more likely the top of the cartridge clip guide, you can modifiy the aperture slide so it goes lower.

The way to do this is to file/grind off the very front of the aperture slide. Since I have no way of knowing how high your aperture hole sits, there is no way I can give you a measurement to take off the front of the slide. I can tell you that I have taken 1/16" to 3/32" off the front of the slides I have worked on before and only a couple of times had to go further back than that. What you need to do is cut the front end a bit and then run the aperture all the way down and check to see the aperture hole is still above the level of the cartridge clip guide. This can be sort of difficult as you will cut the front so it matches up to a vertical wall and the slide is curved. What I do is grind the slide a little and then put the slide back into the rear sight base. Then I lay the base and slide on a board or fleat surface and file the front of the slide vertical. You want to stop grinding/filing before top of the cartridge clip guide can be seen in the aperture hole. However, if you cut a bit too far, don't worry as it can still be used. You will just have to put a click or two of elevation on it before you use it for shooting. Even with shortening the aperture slide like this, I doubt you would ever have a problem running out of elevation at 500 yards, which is the effective range of the standard infantry (not NM) M14. You can slso silver solder a strip of metal onto the top of the front sight blade if the rifle still shoots too low, though I have rarely run into that.

Something I did not mention that can go wrong is if the nut in the windage knob does not screw around the end of the pinion correctly. On a very few occasions, I've seen that nut screwed down tight and the elevation was not distinct or was too tight to move the windage knob. Though this is NORMALLY caused by a worn out spring in the elevation pinion, this CAN be caused by the nut in the windage knob. That nut is held in place by a "C" spring that goes in a groove around the nut and into a groove inside the windage knob. In the old days when that happened, we just grabbed another windage knob because the nuts and springs were not separate repair parts in the military supply system. However and even though they made a bazillion windage knobs for Garands and M14's, the supply is running low as so many have been used to build new commercial M14's. Today it is becoming economical to repair windage knobs and NM windage knobs when the nut and or spring wear out. Hueygunner on this forum has the nuts and springs for sale and will also mount a new one, I'm informed. That is great news.

OK, I "think" I have covered about everything on standard Rear Sights. Will begin on NM apertures in the next post.
 
#26 · (Edited)
Part VII Installing NM Hooded Apertures.

First allow me to say that this is almost always NOT a "Drop In Part" and don't let anyone tell you so. Even when one puts them in standard bases, there is often at least some work to do on the rack or slide of the aperture.

I have long since forgotten just how many of these I have installed on real NM M14's and semi auto commercial M14's. I don't think I'm exaggerating when I say the number is probably between 2,000 to 3,000 or more. (The one thing I'm sorry I did not keep track of on active duty was just how many NM M14's I built or rebuilt.) With a WHOLE lot of mistakes made and that much experience, I am pretty obstinate about how and in what order these things should be fitted.

Most of the ones I fitted were those contracted for by the military and they should always be considered "best quality." I have fitted two of SEI's sets and they meet that criteria as well. I buy a lot of Fulton Armory's hooded apertures these last few years. The rack or slide portion on those are cast, but they are pretty good quality and well worth using. (BTW, the later military contracted NM hooded apertures ALSO had cast slides, so I'm not against a cast part here.) I have not yet tried Krieger's hooded apertures, but I am going to order some and I expect them to be at least as good as Fulton Armory's. However, most of the rest of the civilian copies are poor to downright junk and I would NOT buy or use them.

There are two sizes of NM Hooded Apertures the .520 and .595. Now, this is NOT the actual size of the hole as they left out a ZERO of the actual size. However, that's the way NM apertures have been marked since even before they had hooded apertures. (The NM non hooded Garand apertures were marked this way as well.) You use the .595 with the standard front sight and the .520 with the thinner NM sight on either the Garand or M14. I have found OVER 90 percent of all shooters do better with the .595 hood and standard front sight and that's from over 35 years of switching them back and forth for shooters. My suggestion is that if you are 30 years old or more OR if you wear glasses - then use the .595. I proably install 20 .595 apertures for every ONE .520 size. I normally don't even keep a .520 size in stock as I get so little call for them, but if I do, I only keep one.

OK, so I guess I should first mention you should inspect how the hood turns on slide before you even begin to fit it. Good hoods will have good spring tension holding the hood in either the up or down position as you turn them 180 degrees. Hoods that don't have good tension can certainly be fixed thanks to Art Neergard.

At Camp Perry this year, I traded Art for a bunch of the tiny springs and detent balls, round springs, clips and his excellent little holding fixture. Man that holding fixture is nice!! Wish we had come up with something like that over 35 years ago! There are four things you need besides the fixture. You have to modify a set of snap ring pliers to fit the rectangular holes in the clips to spread the clips apart. You also need a good set of tweezers to hold the springs and ball bearings. I found you need a small jeweler's screwdriver. The other thing I found extremely useful is a section of an M1/M14 cleaning rod.

If the hood is loose or wobbly and still has the C clip on it, you must first take off the clip using the modified snap ring pliers. Throw the old clip away as it will not hold tension if you try to re-install it. The round spring on the front face of the aperture will come off and slowly and carefully pull the hood to the rear. There are two TINY ball bearings and springs that go into two holes in the hood. I prefer to put new tiny springs in when I rebuild a hooded apertures and usually you will lose or need to put new ball bearings in them as well. I figure if you are going to rebuild it, better to put in new parts. The SECRET to getting the tiny ball bearings to stay put is to use a tiny dab of grease on them. I used a dental pic to put the grease dabs in place. That will keep them in place.

I don't know how Art does it, but I used my smooth jawed machinist's vise to hold the rod that the delron bushing goes around and you put the hooded aperture rear side down on both of them. You need to take a little time to get the rod so the rear of the aperure just fits down on the vise jaws so it won't wobble around as you remount everything. I had to use a small jewelers screwdriver to get below the rod to hold it at the right place while I tightened the vice jaws.

I had not rebuilt any hoods in about 9 years and found my modified slip ring pliers were just a bit large. OK, a little filing with a jeweler's file got them back into the correct shape to fit the retangular holes in the C clips. After I spread the C clip slightly to go over the post of the hood, I pushed down on it with the pliers on one side and a jeweler's screwdriver on the other side of the C clip. You have to do this because you are pushing against the round doughnut shaped spring on the front of the hood Then I grabbed the cleaning rod section and put the end with the hole over the clip and pressed it down until the clip snapped into place. Now, I wish I could tell you that I did it the very first time. NOPE, I can almost going to guarantee you are going to drop the C clip at least once. After I got one C clip on and it closed in place, I turned the hood to ensure everything was correct and the C clip came off. Not every one of the clips as manufactured is going to work, folks. That is not Art's fault and is just a fact of life. It took three C clips before I got one to work correctly on one hood and two on another. That's probably why Art gives you more than one C clip in his rebuild kit. Also, you can lose the tiny springs, ball bearings or even C clips on the shop floor if you drop them. Yep, been there and got the T shirt many times. Grin. I realize by the ROE's of this board that we are not supposed to advertise in the regular threads, but I hope this will be allowed in this case. Art is the only one I know of who has the parts and the handy fixture and is a forum member as well.

Now, on a new hooded aperture, you should not have to rebuild it. If when you turn the hood and it does not spring nicely into position, then I would return it. I have not had that problem with any of the manufacturers of NM hooded apertures I have recommended, though. If you have a choice between two or three at a gun show for example, I would choose the one that has the best spring tension as you turn the hood, though.

Special Note; There are going to be at least one if not two or more posts on this subject, so "stay tuned" for updates.
 
#27 ·
Part VIII More on NM Hooded Apertures.

Once we know the hood has good spring tension and adjusts around well, it is time to try the fit in the RS Base by sliding or attempting to slide the aperture slide into the Base.

Real, G.I. slides were made wider than the width of the slot in the RS base and you had to file/stone the sides down to get them in a NM Base. Some commercially available Hooded Aperture slides will slide down at least part way or all the way into a base. Even when they slide all the way down, you will probably feel some friction along the travel. In a standard RS Base, many slides will slide with some friction to easily all along the length of travel in the base.

OK HERE IS A TIP FROM HARD WON EXPERIENCE. Usually, the G.I. slides would not hang up on the teeth section of the slide against the sides of the bottom slot in the RS Base. The teeth were a bit narrower than I have seen on many more recent commercial NM Aperture slides. Back in the early 70's when I was going through my OJT apprenticeship program, I did not realize the sides of the teeth could rub and bind against the RS base and I was not taught about that. The teeth would rub when we annealed the RS base and peened them tighter by effectively squeezing the base against the sides of the aperture slide. I had some epic battles lapping in NM aperture slides before I figured that out. Of course when I became the Instructor of OJT's (Apprenticeship Instructor) I did teach that to all my OJT's. OK, so why does that matter? Glad you asked.

It is Very, VERY common on new commercial NM Hooded Apertures for the sides of the teeth to rub/bind when running the slide up and down. in the RS base. Even if you can get the slide to move throughout it's length, we do not want rubbing or binding there as it makes fitting a RS base harder and will cause the sight to bind up when you go to adjust elevation or windage.

With this in mind, we need to use black magic marker or dykem blue on the sides of the aperture slide AND both sides of the teeth all the way along the slide and then run the aperture in the RS base. I can almost guarantee you it will show rub marks on at least one side of the teeth. THE FIRST THING YOU FILE IS THE SIDE/S OF THE TEETH THAT SHOWS RUBBING MARKS. After you file the teeth flat on the sides a little, then remark the sides of the teeth and run it through the RS base again. If it is still rubbing, file it more until there are no rub marks on the sides of the teeth. The teeth should not contact the side of the slot in the RS Base.

Once you get the sides of the teeth filed so they don't rub, many commercial NM aperture slides will move all the way down and up freely in a standard RS Base. (Even on many unmodified NM RS bases, the commercial NM aperture slides will move up and down with no friction or very little friction once the teeth are filed clear.)

If you are fitting a NM Hooded Aperture to a Standard RS base and the slide freely moves up and down with no friction, DO NOT file the sides of the slide unless there is noticeable friction or catches. Maybe half of the commercial NM hooded apertures will work in Standard RS bases this way. If there are noticeable catches or friction points, then we have to move to the sides of the slide.

In theory and in a perfect world, the sides of the aperture slide would be absolutely parallel and the exact same width from top to bottom. That would make it almost unbelieveably simpler to fit an aperture slide so it would be tight all the way along it's travel in the RS Base. Unfortunately we don't live in a perfect world. Even the sides of the original G.I. NM aperture slides were not perfectly parallel, though they normally only varied by only one or two thousandths of an inch along their length. Commercial NM aperture slides can and do often vary more than that. The more the sides of the aperture slide are not parallel, the more difficult job you have of fitting them. You REALLY need a set of good dial calipers or a micrometer to check the width along the length of the slide for doing a lot of NM aperture fitting, but you can get along without them for just fitting a NM aperture in a standard base.

If you look at the rub marks left on the sides of the slide, you may be surprised how little contact or rub marks there are. Usually one side shows more rubbing along the length than the other. That's OK for now. What we NORMALLY run into is the slide gets tight right as the Hood gets close to going all the way down. (This was even quite common on the G.I. Hooded Apertures.) So look for rub marks on both sides of the slide that are near the Hood at the very top of both sides of the slide. AGAIN FROM HARD WON EXPERIENCE, this is the area that causes people the most problems and expecially when they are new to fitting NM hooded apertures. If you have a set of dial calipers, you should see the width gets wider near the Hood when you see the rub marks there. We need to take down the width of the slide when we see those rub marks at the top of the slide BUT we have to do it carefully. Some folks may think to use lapping compound to do it, but my advice is DON'T LAP IT YET. Lapping at this point would cause the slide to loosen up too much over the entire length of travel. What we need to do is get the wide upper portion of the slide down to the width of the rest of the slide FIRST. At this point, I wrap a couple of layers of masking tape around the hood so you don't file or grind on the finish of the Hood if you slip up.

Remember we want to keep most of the side of the aperture slide the same width. OK, so how best to work down the high spots near the very top of the slide? Well, I have found you DO NOT want to try filing or stoning flat along the entire side of the slide. It is just TOO easy to cut even more off the width of the lower part of the slide. Most of the time I use a 1/4" wide Medium India Stone on both sides of the top BUT HERE'S THE TRICK, you stone perpendicular or at a right angle to the length of the slide because we just want to work on the very last upper portion of the slide. What I do is place the end of the stone right at the end of the slide and press down harder on the side that is close to the hood. You do this on both sides of the top of the slide if both sides show rub marks. By pressing down harder towards the hood side, it will take more metal off at the very top of the slide. I stone about five strokes and magic mark the slide and run it through the base.

DON'T FORGET to magic mark the sides of the teeth and clear any high spots on them when you are doing this.

Now, if there is a difference of two or three thousandths of an inch in the width of the slide near the hood vs the rest of the length of the slide, then you are going to have to use a very fine cut file like a flat needle file AND you file perpendicular (like the stone) and put more pressure on each side towards the hood. NOTE: (On your very first time you fit a NM hooded aperture, it is not a bad idea to completely fit it with a stone and not a file. You usually can't screw up the side of the slide so badly with a stone as a file.) When you are close to getting the high spots cleared, you go back to smoothing it with the 1/4" wide India stone to smooth out the filing. When the high spots are gone, you need to slightly round the corner of the top of each side of the slide so it is not sharp and won't dig in. I want to make this clear, we have not as yet touched the REST of the length of the sides of the slide. You will probably find that is all you have to do to get a NM Hooded aperture to run smoothly in a standard RS base.

OK, so what if the slide will only go down part way or will barely start in the groove in the RS base? That probably means the entire width or much of the width of the slide is too wide. Folks, at this stage UNLESS you are fairly accomplished with hand tools, it would probably be better to have someone do the work who knows how to do it. For example, I have the basic mechanical knowledge to work on automobiles or heating systems, but I DON'T work on them because I do not have the training, experience or tools. So if I haven't scared you off at this point, we will go on.

You REALLY must have a set of dial calipers or micrometer at this point because you need an accurate measurement of the width of the slide all along it's length. You should measure at the bottom, middle and top of the slide to see how much it is flared in width. You ALSO need to measure the width of the groove in the base with the dial calipers to see about how much you have to take off the width of the slide. YOU SHOULD STILL WORK ON THE VERY TOP OF THE SLIDE SIDES FIRST , though you can not get the slide into the RS base. I get the very top or last 1/4" of the slide worked down to the smallest measurement of the width of the rest of the slide. THEN I stone or file along the length of each side. But there is a trick to how I do that as well.

Let's say the difference between the width of the aperture slide and the width of the groove in the RS base is .005". You DO NOT want to take a full .005" off the width of the side of the slide yet, though. What I do is take out a 1/2" wide Medium India stone and lay one side of the slide flat on it. I sort of rub the slide on the stone in a small circular motion and making sure the pressure is equal all along the length of the slide. Just make sure the hood doesn't touch the stone as you do this. I don't want to take much off it yet, though, just work the finish off a little. Then I flip the aperture slide on the other side and do that side a little bit. That MAY well show you one side of the slide is flatter than the other and that's what we want to know at this point. The flatter side is going to become our reference point, once we get it flat with the stone or even a very fine file - IF AND ONLY IF you are that good with a file and most folks are not. Once find the flatter side and get it flat, THEN AND ONLY THEN will we begin taking metal off so the slide will fit in the RS Base.

Once we have a good flat side and let's say we have to take a full .005" off the width of the aperture slide to get it in the base, then we should flatten the other side (that is not as flat) AND keep it parallel with the original flat side. We need to keep checking width at the bottom, middle and top of the slide to ensure it is parallel. We want to take up to .002" off that side and keep it parallel to the original flat side. Then when we have that accomplished, we move to the original flat side and take about .002" off that side. The intention is to keep the Hood and toothed portion of the aperture more or less in the center of the width of the groove in the RS base for the aperture slide. At this point, we should begin to see the slide will enter the groove on the RS Base. We need to once again use magic marker on both sides of the slide and both sides of the teeth.

The next object is to get the slide to run all the way up and down in the RS base and it probably will require some hard pushing at first. That is good. We need to keep taking off any rub spots we find on the sides of the teeth BEFORE we take metal off the sides of the slide, though. Again, we do NOT want the sides of the teeth to contact the RS Base. Use the dial calipers as you STONE the sides of the slide where the rub marks show and OFTEN check the progress after using the magic marker. You MAY find a high spot in one or both of the side grooves in the RS Base that the alide hangs up on. You can use a small needle file to take them down a bit. You REALLY have to be patient and go slowly in this work or the slide will not have a tight fit.

Some folks use a heavy lapping compound when they reach the point they can push the aperture up and down with a hard shove. I, personally, have found you lap in more problems than you help. I prefer to get most of the friction taken care of by careful stoning on the slide and hitting the high spots in the grooves with light filing. Once the slide moves fairly freely up and down and still with some friction, then I will use 600 grit, non embedding lapping compound to get the final fit. One thing to note about lapping though is you STOP lapping before the slide moves extremely free in the RS Base. When you clean the lapping compound out, it will move freer than with the compound in. It is better to clean out the lapping compound thorooughly and check it and find you need to lap a little more lapping than it is to lap so much the slide is too loose.

What you are aiming for is the slide will move all the way up and down in the RS Base with almost no friction and when you hold the base in the fingers of one hand and the hood in the other hand, the slide will not move barely at all side to side.

OK, we are not done working on the slide yet, but this is a good place to stop until the next post.
 
#28 ·
Pardon me for skipping about a bit, but since I already typed part of this in another answer elsewhere on the forum, I figured I would add it here so I wouldn't have to retype it.

The subject of this post is "Annealing the RS Base" so you can squeeze/pound/tighten it down against the sides of the Aperture slide."

OK, before I go further, I have to point out it is ILLEGAL to do this modification on a John Garand Match Rifle or any rifle where the rules state it has to be in "as issue condition." It IS legal for NRA NM Service Rifle classification and of course if you don't shoot in these competitions, then it does not matter. HOWEVER, don't go tightening the RS Base to aperture slide fit and shoot it in John Garand Match competition and then say I said you could use it in that match. You can't, it is not legal. The reason it is not legal is because no standard military Armorer was EVER allowed to do this on either a standard Garand or M14 rifle - it was only done on NM, DMR and some highly specialized rifles.

If anyone wishes to try this out, I MOST strongly suggest you do it with a standard RS base before doing it with a NM RS base. Standard RS bases cost much less than NM bases and is the better part to learn on.

I lay the RS base on the anvil portion of my large machinist's vise and heat it with an oxy acetylene or even a combination MAPP Gas and Oxygen torch. I would NOT suggest you do it with a common propane torch as it takes too long to heat and you will actually anneal more of the metal than we want. Some folks hold the RS base "by the ears" in the jaws of a SMOOTH jawed vise and you can do it that way as well. You will need a pair of pliers to grab and move the hot RS base after you heat it.

The color you want is a bright cherry red. DO NOT quench it after heating it as it can twist like a pretzel and then you will ruin it. After heating, just set it on a concrete floor, fire brick or thick piece of scrap iron or steel and let it cool naturally for about 1/2 hour. You can not reharden it after fitting the NM aperture as you most likely will get heat distortion and then you would have to lap it again. We never rehardened NM RS Bases and they stayed tight for QUITE some time for our NM shooters who shot over 120 rounds a day for amost three straight months. We ocassionally had to retighten and relap a few RS bases every year after all that shooting, but not nearly as many as one would think. I've seen them stay tight on civilian used rifles for five years or more to a whole lot more - depending on how much the rifle was shot.

I taught a lot of people to do this and this is the way they almost never screwed it up. What you need to heat is the sides of the RS base grooves that cover the sides and side tops over the outside edge of the aperture slide. Think of it as an inverted "L" shape. THIS IS IMPORTANT!!!! You put the flame on the INSIDE of the RS base at an angle so you mainly heat just that inverted "L" part of the base. You begin at the bottom and slowly move the flame up each side as the metal turns bright cherry red. ALSO, you MUST not stop near the top and you must go behind and above where the groove ends. Otherwise, the base will crack in that area on one or both sides when you tighten the base. It is actually better to heat a little too much metal than not enough. This is going to permanently change the color of the RS base in the area you heat. We never worried about that for Marine Corps NM rifles and civilian rifles we built. It may not look quite as pretty as before you heated it, but pretty is as pretty does. You can refinish the RS base by black oxide (hot bluing) or even parkerizing after you finsh fitting the aperture slide, if you wish. You may need to do a tiny bit more lapping if you reparkerize it, though.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top