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M1A Hammer problem

This is a discussion on M1A Hammer problem within the Gus Fisher forums, part of the Gun Professionals category; Gus, a friend has an M1A on which the hammer always follows the bolt without firing the next round. In other words, after the first ...


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Old November 27th, 2012, 07:16 AM   #1
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M1A Hammer problem

Gus, a friend has an M1A on which the hammer always follows the bolt without firing the next round. In other words, after the first shot the hammer seems to follow the bolt forward (the hammer does not lock in place). It does not do so with any force though as it does not hit the primer with anough force to fire the next round. Needless to say, it makes the rifle a single round weapon. Any suggesttions as to what is causing this problem? Thanks

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Old November 27th, 2012, 08:13 AM   #2
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Not Gus, but -
1) Take the trigger group out of the rifle.
2) Hold the trigger fully rearward, and push the hammer fully rearward. The 'rear hooks' on the hammer should push against the triangle shaped piece at the top-rear of the trigger AND then have the hooks caught under that triangle piece while the trigger is still rearward.

IF the hammer is not caught, then that's the trouble - examine the rear hooks for damage and try to estimate how much distance they miss contact.

IF the hooks ARE caught, then maybe the hammer is not being push DOWN far enough on the triangle piece - perhaps the trigger group sits too low in the stock.
4) As the trigger is allowed to move forward the hammer is released by the rear triangle and must be caught again (called the handoff) by the front hooks.

Tell us what you find....

Jay Kosta
Endwell NY USA

Thanks from 4Quangs
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Old November 27th, 2012, 03:38 PM   #3
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Will do, thanks.

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Old November 28th, 2012, 09:11 AM   #4
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There are six main/usual causes of a hammer following the bolt, or IOW, not resetting properly. I will list them in the order of the most common reasons first and the least common reasons on down the list.

1. The sear on the M14 trigger assembly goes wide way out to the right side. That was for the full auto feature. If the stock does not have the vertical channel that is a clearance for the sear tail (just ahead of the rear bedding surfaces for the rear of the trigger housing), or one that is not deep/wide enough, the wide M14 sear tail will rub on the stock and can/will cause it not to reset.

You can check to see if the sear tail is contacting in the stock by putting a layer of grease on the right side of the sear and mount the trigger mech back in the rifle. Dry fire it about 5 times and recock the hammer by pulling the op rod to the rear.

The fix is to either use an M1 trigger assembly that does not have as wide of a sear OR cut the end of the M14 sear tail off with a Dremel Cut Off Disc. It needs to be as wide as an M1 Sear, but it can be just a bit wider. The important part is the sear has to be wide enough the right hammer hook fully engages it. So if the sear is just a bit wider than the right hammer hook, then you are good to go.

2. Damage to the Hammer hooks and/or trigger and sear assembly. If the hammer hooks are chipped or broken, then the fix is replace the hammer. The trigger assembly can also be chipped and replace it if that is the case.

3. This next one used to show up quite frequently on Boyd's or other commercial stocks. It can also happen when someone incorrectly glass beds the rear of the trigger housing too low. What causes the hammer to follow is the rear of the trigger housing is TOO LOW when it is locked in the stock. That means the bolt can not force the hammer down far enough for the sear to engage properly.

Take a pair good dial calipers and put them inside the stock. You measure from the two small bedding surfaces for the rear of the trigger housing up to the top of the stock where the receiver heel sits. This distance on an M1 Garand or M14 is supposed to be NO MORE than 1.725" and may be as little as 1.700". On some Armscorps and LRB receivers I have run across, I had to bring this distance down to 1.690" because parts of the receiver were not to spec. If the distance is OVER 1.725", then you have to cut/par a little wood off the two small bedding surfaces in the stock for the rear of the trigger housing, until the distanceis 1.725" or less.

4. This next one is a little hard to describe and understand. Take the trigger group out the stock and look at the stock between the two small bedding surfaces for the rear of the trigger housing. There is a groove between those two small bedding pads in the stock. Look for an indentation at the front of that groove. The indentation comes from the trigger hitting the stock when this groove is not cut high enough and does not allow the trigger to move enough so the sear can reset. It is easier to see the indent on a wood stock, though you may not see it on a wood or fiberglass stock. Put a little grease on the back of the trigger where it is just above the bottom of the trigger housing. There is a sort of a triangular shape there and grease the top of the triangle. Put the trigger housing back in the rifle and dry fire it a few times and then take the trigger housing out. If there is a grease spot left on the stock between the two small bedding pads, you have to cut at least the front of the groove higher so the trigger does not hit it.

5. Someone did a trigger job and either they went too far or the trigger wore down to the point it is too light. Sooner or later with enough rounds fired, even the best trigger job is going to wear light. In this case, you get a piece of 320 grit Garnet (cloth backed) sand paper for metal. Take the trigger mechanism out of the rifle and allow the hammer to go fully forward. Pull back on the sear and slip the Garnet paper between the sear and the rear of the trigger with the GRIT SIDE of the Garnet paper facing forwards. Let the sear go forward - tight on the Garnet paper. Pull the Garnet paper out to either side. This will cut a little off the rear of the trigger assembly and will increase the sear engagement. It may take two to four times pulling the Garnet paper to take enough material off the rear of the trigger assembly to increase the sear engagement and the trigger pull will increase in weight.


6. The rear of the bolt is chipped or worn down too much and it does not push the hammer far enough down to reset. If the bolt is chipped or worn down severely, you have to replace the bolt. This is very uncommon, except in the case of the soft M14 Chinese bolts.

7. The "D" shaped cuts in the receiver legs were not machined cleanly/correctly OR they were made too low on the receiver legs. I have seen this in Armscorps and LRB receivers more than in other commercial receivers. So what happens is when you get enough distance between the receiver and the front bedding surfaces of the trigger housing that you get good lock up of the trigger guard, the rear of the trigger guard is now too low and does not allow the bolt to push the hammer down far enough. OMG can these be a PITA to fix. What you have to do is glass bed the trigger housing at an angle where the front of the trigger housing is low enough to get good trigger guard lock up, but the REAR of the trigger housing is high enough that the bolt can drive the hammer down enough to reset.

Thanks from budster, 4Quangs and Quis ut Deus
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Old November 28th, 2012, 12:24 PM   #5
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Quote:
Originally Posted by Gus Fisher View Post
There are six main/usual causes of a hammer following the bolt, or IOW, not resetting properly. I will list them in the order of the most common reasons first and the least common reasons on down the list.

1. The sear on the M14 trigger assembly goes wide way out to the right side. That was for the full auto feature. If the stock does not have the vertical channel that is a clearance for the sear tail (just ahead of the rear bedding surfaces for the rear of the trigger housing), or one that is not deep/wide enough, the wide M14 sear tail will rub on the stock and can/will cause it not to reset.

You can check to see if the sear tail is contacting in the stock by putting a layer of grease on the right side of the sear and mount the trigger mech back in the rifle. Dry fire it about 5 times and recock the hammer by pulling the op rod to the rear.

The fix is to either use an M1 trigger assembly that does not have as wide of a sear OR cut the end of the M14 sear tail off with a Dremel Cut Off Disc. It needs to be as wide as an M1 Sear, but it can be just a bit wider. The important part is the sear has to be wide enough the right hammer hook fully engages it. So if the sear is just a bit wider than the right hammer hook, then you are good to go.

2. Damage to the Hammer hooks and/or trigger and sear assembly. If the hammer hooks are chipped or broken, then the fix is replace the hammer. The trigger assembly can also be chipped and replace it if that is the case.

3. This next one used to show up quite frequently on Boyd's or other commercial stocks. It can also happen when someone incorrectly glass beds the rear of the trigger housing too low. What causes the hammer to follow is the rear of the trigger housing is TOO LOW when it is locked in the stock. That means the bolt can not force the hammer down far enough for the sear to engage properly.

Take a pair good dial calipers and put them inside the stock. You measure from the two small bedding surfaces for the rear of the trigger housing up to the top of the stock where the receiver heel sits. This distance on an M1 Garand or M14 is supposed to be NO MORE than 1.725" and may be as little as 1.700". On some Armscorps and LRB receivers I have run across, I had to bring this distance down to 1.690" because parts of the receiver were not to spec. If the distance is OVER 1.725", then you have to cut/par a little wood off the two small bedding surfaces in the stock for the rear of the trigger housing, until the distanceis 1.725" or less.

4. This next one is a little hard to describe and understand. Take the trigger group out the stock and look at the stock between the two small bedding surfaces for the rear of the trigger housing. There is a groove between those two small bedding pads in the stock. Look for an indentation at the front of that groove. The indentation comes from the trigger hitting the stock when this groove is not cut high enough and does not allow the trigger to move enough so the sear can reset. It is easier to see the indent on a wood stock, though you may not see it on a wood or fiberglass stock. Put a little grease on the back of the trigger where it is just above the bottom of the trigger housing. There is a sort of a triangular shape there and grease the top of the triangle. Put the trigger housing back in the rifle and dry fire it a few times and then take the trigger housing out. If there is a grease spot left on the stock between the two small bedding pads, you have to cut at least the front of the groove higher so the trigger does not hit it.

5. Someone did a trigger job and either they went too far or the trigger wore down to the point it is too light. Sooner or later with enough rounds fired, even the best trigger job is going to wear light. In this case, you get a piece of 320 grit Garnet (cloth backed) sand paper for metal. Take the trigger mechanism out of the rifle and allow the hammer to go fully forward. Pull back on the sear and slip the Garnet paper between the sear and the rear of the trigger with the GRIT SIDE of the Garnet paper facing forwards. Let the sear go forward - tight on the Garnet paper. Pull the Garnet paper out to either side. This will cut a little off the rear of the trigger assembly and will increase the sear engagement. It may take two to four times pulling the Garnet paper to take enough material off the rear of the trigger assembly to increase the sear engagement and the trigger pull will increase in weight.


6. The rear of the bolt is chipped or worn down too much and it does not push the hammer far enough down to reset. If the bolt is chipped or worn down severely, you have to replace the bolt. This is very uncommon, except in the case of the soft M14 Chinese bolts.

7. The "D" shaped cuts in the receiver legs were not machined cleanly/correctly OR they were made too low on the receiver legs. I have seen this in Armscorps and LRB receivers more than in other commercial receivers. So what happens is when you get enough distance between the receiver and the front bedding surfaces of the trigger housing that you get good lock up of the trigger guard, the rear of the trigger guard is now too low and does not allow the bolt to push the hammer down far enough. OMG can these be a PITA to fix. What you have to do is glass bed the trigger housing at an angle where the front of the trigger housing is low enough to get good trigger guard lock up, but the REAR of the trigger housing is high enough that the bolt can drive the hammer down enough to reset.
Excellent post, most of the time it's number one as someone tries to put a USGI trigger group in a commercial stock.

I think SAI uses a commercial copy of the M1 trigger in their M1As

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Old November 29th, 2012, 09:29 AM   #6
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Gus,

Thank you for answering these questions! You make this site a wonderful resourse for those of us new to M14/M1A shooting.

Bob...

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Old November 29th, 2012, 09:54 AM   #7
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Thank you Gents.

I should have mentioned that in almost every single case, with the exception of a trigger mechanism that has already had a "trigger job" done on it and then a little work may have to be done, the M1 trigger and sear assembly is totally interchangeable in the M14 trigger assembly.

From the earliest use of GI NM M14's, we used M1 Garand Trigger and Sear Assemblies OR cut the wider M14 sears down to the width of M1 Sears. We did that as part of the National Match Modification of EVERY NM M14 so the wider M14 sear would not drag/rub on the stock and cause failures to reset.

Thanks from budster
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Old December 12th, 2012, 06:36 PM   #8
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#3 was it on the Boyd's stock. Rear of trigger group was sitting too low in the stock. Thanks Gus and all for your help on this.

Thanks from tonyben
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Old December 13th, 2012, 09:58 PM   #9
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Quote:
Originally Posted by Milwroad View Post
#3 was it on the Boyd's stock. Rear of trigger group was sitting too low in the stock. Thanks Gus and all for your help on this.
You are most welcome.

Thanks from tonyben and budster
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