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Trigger Group Lock-up, how tight is too tight?

This is a discussion on Trigger Group Lock-up, how tight is too tight? within the Gunsmithing forums, part of the M14 M1A Forum category; Newbie needs advice on trigger group fitting. I have a new LRB receiver, and a virtually new, unmarked, CMP trigger group. My stock is also ...


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Old June 23rd, 2013, 08:08 PM   #1
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Trigger Group Lock-up, how tight is too tight?

Newbie needs advice on trigger group fitting. I have a new LRB receiver, and a virtually new, unmarked, CMP trigger group. My stock is also unmarked. I read on this forum that one needs quite a bit of pressure to lock up the trigger group. I'm bending the guard and nothing is locking up. I used nail polish on the trigger cams to see where they contact the receiver legs. Please view my photos to make more sense. I have about 1/32" of wood below the stock liner at the trigger pad area. I have about 1/16" between the bottom of the receiver legs and the top of the trigger group as seen in the photo. I have about 1 3/4" of wood as measured from the top of the stock to the bottom of the trigger pad area. It seems to me that material needs to be removed, somewhere. I appreciate your help and advice. My first post so please be patient. Thank you, photos are attached.
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Old June 24th, 2013, 04:46 AM   #2
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The trigger guard should need some force to fully close & lock, but certainly not so much to 'bend the trigger guard'.

When the guard is being swung closed, does it engage the lugs in the receiver and pull the receiver against the top of the stock?
Or, does is 'jam' and not pull down on the receiver?

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Old June 24th, 2013, 07:15 AM   #3
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Thanks Jay. I've put a few M1's together and know what it feels like to get that nice crush feeling when you swing the guard closed. This group stops cold and does not engage the legs of the receiver. The tip of the guard is about 5/8" from the tip of the trigger, and, about 1 1/2" from the tip of the guard to the bottom of the trigger group. I can see the guard bending when I try to close it. I really don't want to distort the guard, so I stopped and am now seeking a professional's opinion. I put nail polish on the round surfaces of the locking cams and as seen in the photo, there is a mark high on the cam, where I put the red tape. To me, this seems too high to engage the legs. Thank you again.

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Old June 24th, 2013, 03:12 PM   #4
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OK, this MAY sound like a silly question, but have you tried putting the trigger mechanism in the receiver WITHOUT the stock and locking down the trigger guard? It should lock down easily and once locked down, it should be a little loose up and down.

If the trigger guard does not lock down easily with no stock in place, THEN the "D" shaped cuts in the receiver legs, that the trigger guard locks into, are TOO HIGH. I found this in a few early LRB receivers.


Last edited by Gus Fisher; June 24th, 2013 at 04:14 PM.
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Old June 24th, 2013, 03:25 PM   #5
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Sorry, hit the send button too soon.

With the GREAT pictures you posted and especially the top middle one that shows the triggerguard 5/8" from the tip of the trigger when it stops, yes, that is too far away.

If the trigger guard does lock down easily in the receiver when there is no stock in place, the next thing I suggest is smear a thin coat of grease on the underside of the receiver heel and the two long bedding surfaces forward of that (these surfaces are meant to fit on top of the stock). Then put the receiver in the stock and push down hard on the receiver. Take the receiver out and see IF AND WHERE the grease rubs show contact on top of the stock.

You see in a case like this, we have to figure out:

1. If the receiver is not going down properly on top of the stock
or
2. The stock liner is not allowing receiver legs to go down far enough
or
3. You may just need to file some wood off the bottom of the stock under the front pads of the trigger housing.

Please DON'T cut the stock until you check these things and let us know "what is happening" with your stock and possibly trigger mechanism fit to a bare receiver.

Thanks from JayKosta and MemphisMachinists
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Old June 25th, 2013, 05:19 AM   #6
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Thank you for the reply. I did fail to mention, without the stock, the trigger group locks up easily in the receiver. I will try your advice tonight after work. Do the bottom of the receiver legs typically contact the top of the stock liner on a properly fitted M14? I have about 1/16" gap between the bottom of the receiver legs and the top of the stock liner as measured with a 1/16" drill bit, as seen in photo. I will post after following your advice, thanks again.

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Old June 25th, 2013, 06:25 PM   #7
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Good Evening Gentlemen,
I believe that I have a contact problem on the top of the stock. It seems that 99% of M14 photos are taken of the op-rod side. One can see in most of the photos,the cut to match the step / contour of the receiver. My stock shows slight indents, on the top of the stock, where some receiver was in this wood at some time, as well as trigger group pad indents on the bottom. Please review my photos. The light makes some surfaces look wavy, they really are straight. The complete area from the rear of legs to the heal is not supported, approx. 3/64" gap. My machinist's rule shows how flat the top of the stock is. I'm guessing that the entire receiver should be touching wood. Please let me know your opinion. Thank you.
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Old June 25th, 2013, 06:26 PM   #8
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One last photo.
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Old June 25th, 2013, 06:55 PM   #9
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Quote:
Originally Posted by Tomar270 View Post
Thank you for the reply. I did fail to mention, without the stock, the trigger group locks up easily in the receiver. I will try your advice tonight after work. Do the bottom of the receiver legs typically contact the top of the stock liner on a properly fitted M14? I have about 1/16" gap between the bottom of the receiver legs and the top of the stock liner as measured with a 1/16" drill bit, as seen in photo. I will post after following your advice, thanks again.
This is not unusual on GI M14's, though that distance will vary with commercial M14 receivers.

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Old June 25th, 2013, 07:12 PM   #10
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That's not good. There should be wood contact from the rear of the receiver heel going forwards on both sides of the receiver from 1" to 1 1/8". This helps lock down the receiver heel as the bolt goes to the rear and twists the receiver heel in recoil. You can't see it happening even if you watch someone else shooting, but it does happen.

What this looks like is someone else already tried to fit the stock to a commercial receiver, BUT I could be mistaken because I don't have the stock in my hands.

Do the receiver legs stick in the stock liner when you put the receiver in the stock?

Can you grease the long bedding areas of the receiver that contact the top of the stock and push the receiver hard down into the stock and then take pictures of the grease transfered to the top of the stock?

What I'm concerned about is you might not have enough wood on top of the stock and room in the stock liner to "inlet" the front of the receiver down far enough to get contact on both the two long bedding surfaces at the front of the receiver and get good receiver heel contact.

On a stock like this you MAY have to take the stock liner out and fit it to the receiver legs so the receiver can come down further. However, that may not be enough for the receiver heel to contact. Contact on top of the stock can be corrected by glass bedding, though. Even with this I "THINK" the stock is going to have to be cut to allow the trigger housing pads to go up higher.

I don't believe this is going to be an easy fix.

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Old June 26th, 2013, 04:56 AM   #11
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Good morning and thank you. I'll do the contact test after work tonight, mow Mom's lawn if it's not raining after work, always running............

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Old June 26th, 2013, 07:01 PM   #12
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Good Evening, lawn got rained out, had dinner with Mom. With the stock liner removed, the group still won't lock up. Assemble receiver, stock liner, trigger group, everything plays well together, easily, no forcing. I used tape instead of grease to make it stand out better, please view the photos. There is about a 3/64" air gap between the stock and the unsupported part of the receiver. I'm thinking I need to inlay the top of the receiver, a whisker at a time, checking lock-up as I go, until I achieve lock-up; or, full receiver to stock contact. Please comment. Photos attached. Thank you for your wisdom.
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File Type: jpg M14 25.jpg (11.3 KB, 31 views)
File Type: jpg M14 21.jpg (13.3 KB, 30 views)
File Type: jpg M14 22.jpg (12.1 KB, 26 views)
File Type: jpg M14 23.jpg (12.4 KB, 22 views)

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Old June 27th, 2013, 09:15 AM   #13
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Quote:
Originally Posted by Tomar270 View Post
Good Evening, lawn got rained out, had dinner with Mom. With the stock liner removed, the group still won't lock up. Assemble receiver, stock liner, trigger group, everything plays well together, easily, no forcing. I used tape instead of grease to make it stand out better, please view the photos. There is about a 3/64" air gap between the stock and the unsupported part of the receiver. I'm thinking I need to inlay the top of the receiver, a whisker at a time, checking lock-up as I go, until I achieve lock-up; or, full receiver to stock contact. Please comment. Photos attached. Thank you for your wisdom.
Let's see, you have open space between the bottom of the receiver legs and the stock liner for the receiver legs to come down 1/16", correct? If there is only an open space between the top of the stock and the bottom of the rear of the receiver heel of 3/64", then it seems you have room to come down far enough for it to contact. However, other things are going to pop up. I hope I can remember everything here.

1. It looks like you will have to take metal off the top of both rear support columns of the stock liner or the receiver will stop dead on top of the stock liner. You may or may not also have to take metal off the top of the front two support columns of the stock liner, after you take metal off the rear columns, for the receiver to go down far enough as well.

2. The receiver legs MAY bind up from front to rear in the stock liner as the receiver goes down. If so, you only file LIGHTLY on the spots that bind because you want no looseness of the receiver legs front to rear.

3. I want to put this one here because I may not remember it later on. When you inlet the receiver lower like this, the op rod spring may bind on top the the "claw" portion of the front of the stock liner. If so, then you have to file the top of the claw down.

4. I am not sure what is going to happen to the fit of the Gas Cylinder and Front Band to the stock ferrule as the receiver is lowered. I think it will be no problem or even helpful to give you more downward tension on the ferrule to the front band. I am sort of "typing/thinking out loud here." If a problem arises due to lowering the receiver, it can be fixed, but it is something we have to keep in mind.

5. The good news out of what could be problems that arise is that glass bedding the top of the stock will fix something that may go wrong as we go along. Now, that is not something a novice can do easily the first time, but it could be done by someone else if you can't do it.

OK, since you got the liner out of the stock, the FIRST thing to do is fit the liner to the receiver legs so you can take wood off the top front of the stock to lower the receiver in the stock. Along with that, you have to understand that the top rear columns of the stock liner were never intended to touch the receiver when the receiver is put into the stock. That actually makes this EASIER for you.

You are going to need at least one good file and maybe another file to file the stock liner and the stock . The file I recommend you buy is a Nicholson 8" Handy File and you can get them from Lowe's, Home Depot and most other hardware stores.

http://www.lowes.com/pd_96691-273-06...ile&facetInfo=

or

http://www.homedepot.com/p/Nicholson...6601/100208251

This file is FLAT and has one side course and one side fine, which you may/will need to use both sides as you go along. You will also need a file card or a bronze "tooth brush" or even an old worn out bore brush to clean filings out of the teeth as you go along. Now, this file will not fit down inside the stock liner to cut the bottom inside of the stock liner. You would need a file that is not as wide as the Handy File to do that, if necessary. You will also need a large black or red permanent magic marker to mark the liner as you modify it and see where it touches the receiver legs.

It's great you put the stock liner down over the receiver legs in the top middle photo of your last post. This is how you put the liner on the receiver legs to check fit as you file on it. You want to file what are the tops of the rear stock liner columns (when the liner is in the stock) until the bottom of the receiver legs can go down into the stock liner so and almost touch the inside bottom of the stock liner. The front support columns of the stock liner may also have to be filed down a little. ALONG with this as you are filing the support columns down so the receiver legs can go down further, the receiver legs may or may not start to bind up a little on the stock liner. If they do, then gently tap the bottom of the liner with a block of scrap wood to see if the receiver legs will go all the way down. It LOOKS like the front and rear of the receiver legs won't bind much, if any, on the stock liner. If it only sticks a little front to rear, than tapping the liner with the wood block should get it all the way down on the receiver when the liner and receiver are upside down. If it sticks really hard, then you mark the insides of the "U" shapes of the stock liner with the Magic Marker, tap the block down on the liner and file JUST A LITTLE where the Magic Marker got rubbed off. Now don't go hog wild on filing as you want a VERY close fit of the stock liner on the front and back surfaces of the receiver legs. If it the receiver legs stick just a little when their bottom surfaces touch the bottom of the stock liner, that is not a bad thing for right now as the receiver legs going in and out of the liner more times may wear the liner loose without having to file the inside of the "U" of the stock liner.

Note. You can not file metal near as fast as wood, so this is going to take some time to do. You also have to clean the filings out of the file as you go along. After you filed the rear support columns of the stock liner enough the bottom of the receiver legs touch the inside bottom of the "U" shape in the liner and the support columns don't touch the receiver, then lightly angle file on the edges of the support columns you filed so you don't leave sharp edges on the metal. You only need to file just enough to get rid of the sharp edges.

Now a caution to keep in mind. The stock liner is made of mild steel that is not hardened and can be bent rather easily when it is not in the stock. So you have to be careful about holding it when you are filing on it. I suggest you take a block of scrap wood and cut it so it will just go between the width of the distance between the two rear support columns and put it there is you tighten the stock liner in a padded vise to file on the stock liner. If you don't put the liner in the vise, it makes filing a bit more difficult and you should still take care not to bend it. If you DO bend it, the good thing is you can bend it back to shape in your hands, though.

So, file the tops of the rear support columns of the stock liner and the tops of the front columns, if needed, so the bottom of the receiver legs touch the bottom inside of the stock liner "U" section. Do this before you begin filing on top of the stock, on the two long front bedding surfaces, where the receiver is now touching.

AFTER you get this done and reassemble the stock liner in the stock, then you will file wood off the front of the stock where the grease rubs are to lower the receiver into the stock. You have to remember to file where the grease rubs ARE as those are the high spots. You also have to keep contact the same on both sides of the top of the stock. Grease the receiver before every time you try to lock down the trigger guard so it will coninue to leave grease rubs and show you where you will need to file more, as necessary. Don't file a lot at any time before checking. OH, also grease the bottom of the last 1 1/8" of the receiver heel. You are looking to get a "horseshoe" or "U" shaped grease rub from the rear bottom of the receiver heel contacting the stock when you tighten the trigger guard.

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Old June 28th, 2013, 04:41 AM   #14
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Good Morning Gus, I am blown away by your kindness, expertise, and willingness to help. Thank you. I had a feeling that this would be the route to go. I've been a mechanic since the mid '70's; so, between my Father and I, we have ~25 files of all shapes and sizes and quality. Dad was quite handy making wood everything under the sun so I'm sure I have a good selection. I'll start this weekend as time allows and will keep you posted. Thank you for you time and expertise.

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Old July 9th, 2013, 05:55 PM   #15
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Stock Update 9JUL13

Well, I finally have trigger group lock-up. I'll post pics of my progress. My Dad taught me the art of draw filing 50 years ago. Dad used glass, at times, to achieve his shaving goals in woodworking; so, Dad was with me on this project along with his patients as one only has one shot at removing wood. THANKS also to those offering their M14 expertise. I used a protractor to keep the 80* angle needed to match the receiver. The "slab sides?" aided in keeping me parallel and perpendicular. I used the heel as my reference point. I found this pretty nice stock full of tool marks so I had to level the heel first, see photo. I only had to remove the thickness of a machinist's rule as seen in previous photos. Keeping all four planes parallel was a trip to keep the receiver from rocking diagonally as it got closer to the goal. I did remove ~5/64" from the stock channel to give me about .010" between the stock and the op-rod guide. I have about 3/64" air gap to the top of the liner claws. I didn't have to file any legs on the stock liner. I used a bend-a- light to watch my progress as I got closer. When I got a whisker away, I made a press as seen in the photo and steamed the stock for 5 minutes, tightened the bolt finger tight, then 1/2 turn with a wrench, let it sit over night. The next day, I removed the press and installed the trigger group with liner installed. The guard started to bend, I started to swear; then, saaanap, latch, it locked up! Whew, no more whittling! Note the top of the filed area after receiver removal, there is no witness mark from being off angle. Thanks Dad. Now, time to finish the stock and assemble the rifle. The stock to receiver is 97% contact. The only place that allowed light through is through several tool marks as seen in photo. Thanks to all for your expertise. More photos to follow.
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File Type: jpg M14 26 Press 1.jpg (14.3 KB, 31 views)
File Type: jpg M14 27 Press 2.jpg (9.4 KB, 28 views)
File Type: jpg M14 28 Channel.jpg (15.3 KB, 33 views)
File Type: jpg M14 33 Heel.jpg (12.4 KB, 31 views)

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