M14 Forum

tonyben

I wanted to start a thread that can give any average M14/M1A rifle owner a method to give their rifle a quick health check that could help them identify accuracy degrading problems with their rifles. Some problems don't announce themselves with any form of symptom other than the results on the paper downrange.

The tilt test
The first simple health check than can be performed is the tilt test. Since there is already a sticky with a full discussion of the tilt test, I will only post the link..
http://m14tfl.com/upload/showthread.php?t=69061

For those of you who don't know what that test is, believe me, it's well worth reading.

Stock clearance:
Another quick check would be stock clearance all around the barrel. What we are looking for are spots that the wood or fiberglass could be coming into contact with the barrel, op-rod guide or gas cylinder. Remove your hand guard and assemble the rest of the rifle. From there, slide a piece of paper or an index card between the stock and the barrel and move it from front to rear or vice versa...

Look for spots where the paper will not pass. If there is a spot, then the forearm of the stock needs to be sanded or cleared to allow the barrel, op-rod guide or gas cylinder to remain clear of the stock channel. The only spot that the barrel should have contact at the stock is at the front band and stock ferrule. And even then, there should only be contact between the concave and convex surfaces at the bottom of the FB/SF.

The vertical surfaces should have a .010" to .020" clearance between the both of them.

FB/SF alignment:
Another item to check would be the front band to stock ferrule alignment. When looking at the front band from front to rear, there should not be any overhang to the left or right between the FB and SF. If they are not centered, then your rifle needs to be bedded. This will fix the alignment.

Edit: If your alignment is off, then also check that the front band is tight against the gas cylinder. If it's loose, shimming the gas system is in order. In most cases, this will help increase accuracy. See these posts for more on shimming the gas cylinder:

http://m14tfl.com/upload/showthread.php?t=83742
http://www.m14tfl.com/upload/showthread.php?t=67322

Flash suppressor alignment.
Look for copper marks on the front orifice of the flash suppressor. If there are marks, then your flash suppressor needs to be aligned properly. Your bullets may be hitting the flash suppressor on the way out of the barrel and throwing off your shot. This can be tricky so just ask someone here and they will advise you on the proper resolution. A FS strike can crack or break your FS.

Screws and loose hardware:
Check your flash suppressor nut set screw and your front sight set screw to make sure they have not come loose.

Op-rod and gas cylinder alignment:



With your barreled action out of the stock, ease the bolt closed. Look to see that the tail of your gas piston and op-rod are in a straight line. If the op-rod is hitting the GC off center, then the problem could be one of a few things.

1. Your barrel could be over-indexed. If it is, there is not much you can do except have your gunsmith look at it or send it back to SAI
2. Your op-rod guide may be out of alignment. Although there is a pin that retains the op-rod guide, it does not have any alignment function. There is still a bit of play and the alignment can be adjusted.
3. Your splines on the GC and barrel are loose. If this is the issue, then post here and we will help resolve the issue

This is just a quick list to start things off. This post is intended to be one where other forum members can pitch in their list of quick checks that can help other members identify problems before they become problems!

So let's hear your ideas!

Daimyo

Great post. Not a newbie, but well worth repeating.

M1AallTheWay

Excellent! Well worth a sticky.

JAILDOG

Good job, Tony as usual

leadbug

Thanks Tony!

tonyben

Thanks gents. Here are some more inspection tips...

Extractor quick check:
Another quick check is with the extractor. On rare occasions, M1A owners have had their bolt completely disassemble while firing, sending the extractor, extractor spring and plunger into no man’s land. Since USGI extractors are becoming harder to find, rifle manufacturers have had to resort to making commercial extractors. One problem with commercial extractors is that the leg of the extractor can sometimes protrude out the bottom of the bolt too far. It should be as close to flush with the contour of the bolt as possible.

If it is not, the bottom of the extractor leg can come into contact with the magazine feed lips or the next round and it can be pushed upwards and out of the bolt while cycling. To remedy this, you need to file or stone some material off the bottom of the extractor until it is flush with the bolt surface.

Bolt roller impact :
Another rare occurrence is that sometimes the op-rod will travel so far forward that the bolt roller is bound up inside the roller cutout in the op-rod. Normal function should be that the op-rod reaches its full forward travel and the bolt is rotated into full battery. The roller should not have any forward to rear stress. It should merely be resting into battery and being held from rotating by the horizontal surface of the op-rod roller cutout.

Another symptom of this is that the tab of the op-rod will have a rounded forward edge. This means that it is hitting the end of the track for the op-rod. Contact a gunsmith or SAI.

When into full battery, you should be able to wiggle the bolt just slightly front to back, and rotated left to right. The possible causes of this are that your op-rod is traveling too far forward. The common causes of this are the piston being altered to increase dwell time or the barrel may have an out of spec shoulder for the gas cylinder. When the piston reaches the end of its travel inside the gas cylinder, it stops the op-rod from moving forward. This is how the timing is set for the bolt.

Another type of bolt roller impact defect was because of out of spec receivers which did not have enough clearance for the bolt roller. When the bolt rotates into full battery, there should be enough clearance on the receiver that when the bolt lugs are fully bottomed out in the lug recesses, the roller should not be contacting the receiver at all.

To check for this, field strip the rifle. Insert the bolt into the receiver and move it into battery by hand. If the roller is hitting the receiver, you won’t be able to roll it freely. There may also be impact marks on the receiver from the bolt roller. This can damage the bolt roller and cause it to wear and even fall off. To remedy this, go to the sticky section and look up “bolt roller impact defect” by Art Luppino. He gives detailed instructions on how to remedy this. If you don’t feel like you can fix it yourself, send it to a gunsmith or send it back to SAI.

2336USMC

The front face of the stock ferrule should not touch the rear face of the front band. There should be a gap wide enough to easily slide a slip of paper into.

The lip on the bottom of the front band should touch the bottom of the ferrule, with some pressure pulling down on the barrel called "barrel draw." This pressure on a standard rifle should be about 5 pounds or so. For a quick check, put the tip of your index finger on top of the barrel and the tip of your thumb on the bottom of the stock and pinch the two together. It sould take some pressure to make the front band lip pop away from the bottom of the ferrule. The pressure on your fingertips should feel about like the same pressure it takes to pull the trigger.

If this pressure is not there, or is much higher, or if the front band seems to slide to one side or scrape as you pinch, then there is an issue with the bedding or fit of the receiver and trigger group into the stock.

tonyben

Trigger guard lockup:
For the M14/M1A to maintain consistent accuracy, it is typically a unanimous opinion that a tight fitting stock will help maintain accuracy. This is gauged by how tight the trigger guard locks up into the receiver and clamps down on the stock.

A good gauge on the ideal tightness of the trigger guard is when the tirgger guard is latched, you begin to feel tension just as the latch passes the bottom of the trigger as shown in the picture below...

If it tightens before this spot, then there is the risk that your rifle may not function properly and you could have a runaway rifle on your hands. If it's too tight, then the hammer hooks may not engage the sear properly and the hammer can follow the bolt home after cycling, or you may experience doubles. To remedy this, you need to take some material off of the bottom of the stock where the trigger groups wings or pads contact the stock (where the magazine latch is).

If the lockup is too loose and there is little to no tension when clamping the trigger guard down, then your stock fit is loose and your receiver is going to shift around in the stock giving you inconsistent results downrange. In this case, bedding will remedy the problem. Another option is to add some shims under the trigger group wings to tighten things up. These can be made out of aluminum cans or tin foil.

Pvt. Joker

This works ! I had that problem with my first birch stock.

Gus Fisher

Tony asked me to put down what I recommend for minimum length of springs.

Op rod spring minimum length - 15 inches
Extractor plunger spring minimum length - 7/16"
Ejector spring minimum length - 2 inches

If you compete in Matches, I would strongly suggest you put new springs in every year and then you won't have problems caused by springs going bad all year.

Gus Fisher

Tony,

I would also add something about checking the function of the firing pin and safety bridge. I wrote it out in this thread:

http://m14tfl.com/upload/showthread.php?t=62376

Matter of fact, you may want to check that thread for other ideas.

Sigma05

Thanks guys. This was what I was looking for when I joined the forum. I wanted to make sure everything was good before going to the range and maybe making things worse. I found most of this stuff spread out in different parts of the forum. Thanks again for putting it all together in one post. One thing you didn't mentioned and I found on my rifle. Makes sure all the working parts are greased and not oiled.

megathumpzilla

Thanks Gentlemen!

Dave P

Handguard clearance 1): be sure the back end of the HG is not jammed into the receiver. Allow room for thermal expansion/contraction - file it down to leave some room.

Handguard clearance 2): be sure the bottom edges of the HG are not too close or touching the top edges of the stock. I like to have 1/16" clearance between the two, to allow room for "barrel whip".

tonyben

Rear Sight Assembly:

I don't know why I didn't think of this earlier, but check to make sure that your rear sight components are tight. Grab your apperture and see if there is wiggle in all axis. Also, see if your knobs wiggle or if the screws on both sides of the rear sight assembly are loose.

If your apperture can be wiggled up and down, then your apperture or elevation pinion can be worn, This may also be caused by a weak spring (the cover that goes over the apperture and fits into the grooves by the windage marks). In my lubricating post, I posted that the teeth are not to be lubed as this can cause your sights to shift with little vibration.

If you see that your sights are loose in any way, post here and we will help you resolve the problem.

Let's face it, a loose rear sight assembly will severely degrade accuracy!

Gas Port:
It is also a good idea to check the gas port for both obstruction and alignment. If it's plugged, you will be plagued with short stroking or feeding problems.

Pull the op-rod back and lock the bolt to the rear. Tilt the muzzle up until you hear the gas piston slide all the way back. Invert the rifle and lay it in your lap or in a cradle. Insert a 1/16" allen wrench into the hole at the bottom of the gas cylinder. Wiggle it around until you feel it go inside the gas port hole and gently stick it in as far as it will go. BE CAREFUL NOT TO LET THE BOLT STOP DISENGAGE!!! IF SO, THE OP-ROD WILL FLY HOME AND YOU CAN DAMAGE YOUR PISTON AND GAS CYLINDER ASSEMBLY!!! Now that I think about it, it would really stink if your allen wrench sheared and you had half an allen wrench stuck in your barrel. I use a cleaning port to eliminate the risk. You can also throw a block of wood in the action to keep damage from occuring. If you don't want to take that risk, then remove the gas plug and remove your gas piston.

Once the allen wrench is all the way inside the barrel, then look down the barrel and you should be able to see the allen wrench protruding into the barrel. I did this the other day and saw a big glob of carbon lying in the barrel right after I just cleaned it. The allen wrench knocked the carbon build up out of my gas port.

So even if you know your gas port is aligned, it's a good idea to do this from time to time to make sure your port is not clogged.