Help with a family M1 carbine

Hi all,

Hoping someone has experience with an issue and can point me in the right direction. I have a problem with an M1 carbine that seems like the sear won't catch the hammer half the time. When at the range, most of the time the rifle functioned fine. But, sometimes it would chamber a live round and the trigger was dead. I'd eject the round, chamber a new round, and then it would resume working fine. It seemed to work better if the barrel was more vertical when pulling the slide back.

I took it apart at home and saw that the hammer would just follow the bolt home instead of locking back into place. So I cleaned everything up, reassembled, and the problem persisted.

Here's what it looks like:
M1 Carbine - sear wont catch hammer - YouTube

I then ordered the Wolff M1 Carbine rifle service spring pak and replaced the sear spring and the operating rod spring. But, it seems like the hammer is still just a millimeter or two from locking back into place.

Another view:
Imgur: The magic of the Internet

Any tips?

Thanks!

How new is your hammer spring? Is it a wolf spring as well? If it were mine and I'm no expert by the way, the first thing I would check is the hammer spring, it may be just a hair too strong. The sear itself may be getting worn too. Also, I would just change one spring at a time. Process of elimination. Wolf springs may end up amplifying your problems if you change a bunch of springs at the same time in my opinion, you may be creating another problem that you didn't have before.hth

I had the exact same problem. I found the hammer face worn due to poor heat treating or no heat treating. It was an aftermarket part. It was also beating the back of the bolt. I would check both for wear. I would change to another hammer first and see what happens.

Did you replace the sear? Check the sear notch on the hammer? Does the sear move freely when in place in the trigger or are the sides of the trigger binding it. Are you sure your replacement sear spring is good?

If I recall, some sear springs have a smaller end that is the end that goes toward the sear cup. Maybe turn the spring around?

Quote:

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Originally Posted by Pacifist86

It seemed to work better if the barrel was more vertical when pulling the slide back.

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First Welcome to Milsurps Pacifist86,
2nd be prepared for countless pieces of advise now that you've got the hood open.
You'll find a great group here.

I've 'Listened Very Closely' to your video audio and believe I don't hear the Trigger reset Click, until you manipulate the hammer.
Taking in to account what the others have mentioned to check, I'd add making sure your Trigger Spring is oriented correctly... laying Flat on the Triggers rear notch (behind the pedestal). If bent or weak it may be the reason the Sear isn't raising up to catch the Hammer notch.
When your holding the action up..... Gravity may be whats helping cock the Hammer.

Below- Copied and Pasted from: http://www.90thidpg.us/Reference/Man...-1276_1947.pdf

Paragraph 11 Page 12-13 (6) (7) (2)

(6) Engagement of sear with hammer. The sear should engage with
sear notch in hammer when bolt is about halfway retracted. A crisp
click may be heard as sear slides forward into the sear notch in hammer
under force of sear spring. Retract the bolt fully to insure complete
engagement and retention of sear. If click is not heard or trigger pull
appears to be light or excessively heavy, examine sear and sear notch
in hammer for wear, burs, foreign matter in sear notch, or weak or
broken sear spring. Trigger pull should not be under 5 pounds or over
7 pounds.
(7) Engagement of sear when trigger is not released. The sear should
engage and hold the hammer when the trigger is held back and the
slide operated rapidly. Test by grasping the carbine by the grip of the
stock with the left hand with index finger on the trigger. Pull the
trigger all the way to the rear and hold in that position. Grasp the
operating slide handle with the right hand and move the bolt back and
forth rapidly five or six times. Release the operating slide handle in the
forward position, release the trigger, allowing it to move fully forward,
and then pull it again. If the hammer does not fall, it has jarred out of
engagement with the sear and followed the bolt forward. If this is the
case, the carbine may fire full automatic and the firing mechanism should
be inspected for worn or faulty parts.
(2) Trigger. Trigger should move forward under force of trigger
spring when released from rearward position. If trigger does not move
forward positively, trigger spring may be broken, disengaged, or bent.
Trigger hang is also caused by old type triggers with the 4° angle on
the forward face of the pedestal. Test trigger pull as explained in paragraph 13.
TESTING TRIGGER PULL is on page 15-16, reading in part:
a. GENERAL. (1) Test trigger pull for smoothness and for
pressure exerted. Trigger pull should be clean, without creep, smooth
in action; and the force exerted to release hammer should be more
than 5 pounds and less than 7 pounds (See b below.) If pull is rough,
or not within specified limits, or creep is present, it indicates that there
is wear or burs on sear nose, hammer notch, or top of trigger lip, or interference between trigger and housing.
Read All of Inspection Paragraph 31, Starting on page 43....

33. Maintenance and Repair Page 49
b. HAMMER FAILS TO COCK. This condition may be due to damaged
sear, broken sear spring, burs or foreign matter in sear notch in hammer, or failure of bolt to move far enough to the rear on recoil movement to cock hammer. Examine parts; clean and replace if necessary.
c. STONING NOSE OF SEAR. If sear nose or hammer notch becomes
burred or unevenly worn, preventing proper seating of nose of sear in
notch, the burs may be removed in an emergency, and uneven surface
leveled with a fine grained sharpening stone. Stone surface to a polish
only, being careful to maintain angle of face. Stoning should be done
only by trained ordnance personnel. If possible, parts should be replaced by selective assembly.
d. CORRECTING TRIGGER PULL. (1) A light or heavy trigger pull
may be caused by foreign matter or burs in the sear notch in the hammer, on the nose of the sear, on the top of rear end lip of trigger where
the rear end of sear rests, or in the elongated pivot hole in the sear.
Such burs or foreign matter will prevent nose of the sear from seating
fully in hammer notch. To correct, remove foreign matter or stone
burred surfaces to a polish, using a fine grained sharpening stone,
taking care to maintain surfaces, angle, and sharp edges. Replace
badly burred or damaged parts. Stoning should be done only by trained
ordnance personnel.
(2) A light pull may also be due to a weak or broken sear spring
which will not seat the sear fully in the hammer notch before the
pressure from hammer spring is applied to the nose of sear through the
hammer. Correct by removing foreign matter or replace sear spring.
(3) Uneven surface of hammer notch or worn nose of sear may also
cause a light pull. Correct by stoning surfaces evenly, being careful to
maintain angles and sharp corners of faces stoned.
34. Functional Check Page 50-51
a. Cock hammer and check seating and positive retention to limit of sear nose in hammer notch. Continue to retract hammer of rearward
movement and observe forward movement of sear to maintain retention. Sear should continue to contact hammer throughout movement.
Pull trigger; sear should release hammer crisply. Trigger pull should
he from 5 to 7 pounds. Release trigger. It should move positively to
forward position under force of trigger spring and be held there firmly
and without shake even when sear is not assembled. When trigger is in
forward position and hammer cocked, the sear should rest upon or
above top of rear pedestal of trigger.

NOTE: These are the Highlights.... More Info between the lines.

Also View this Video to watch Sear Hammer relationship:

https://www.milsurps.com/showthread.php?t=17368

Keep us updated,

:thup:

Here is a link to a short animation showing the Sear-Hammer interaction.
Sear is the last type..... But works the same as your Sear.

Scroll to bottom of the page:
The U.S. Caliber .30 Carbine Operation & Animations

HTH,

Huge thank you all for the replies!

@jond - I did not replace the hammer spring yet. I saw the new one in the Wolff spring pack was quite a bit longer and did a bit of digging to find that it looked like there were a few different types of these springs. So, I was holding off on changing it (or purchasing an additional/correct one). But great point on only changing one thing at a time to truly find the root cause.

@RWS - worn hammer face would definitely make sense. Just 1mm of wear on the hammer (and likely even less given the angle that the hammer is at when it engages the sear), seems enough to make it finicky.

@W5USMC - I have not yet replaced the sear. It does move freely when installed, but I did notice that it just looked and felt rough when I had the parts disassembled - so probably worth picking up a replacement to test that out as well. Since the same problem persists with both the original and new sear spring I'm hopeful that one (or both) of those are okay.

@DaveHH - great point, and probably the cheapest fix to try immediately. I'll try turning the sear spring around to see if it has any impact.

@painter - huge thanks for pointing to these resources! I have wondered about the trigger spring. When initially disassembling to investigate I found it really difficult to reinstall the trigger spring. That is not a spring that came with the Wolff spring pack, so I think I'll pick one up to try that as well (for $3, why not). It also makes sense that the hammer should engage the sear when the bolt is about half way back. Clearly in my case the bolt is traveling all the way to the rear without the hammer and sear engaging.

Thanks again all! Time for me to get work with the parts I have and picking up a few replacements to try out one at a time. I'll report back the results.

There is another possibility if none of those other suggestions cure the problem. There could be a partial blockage of the gas port. That would contribute to a weak slide operation. In my opinion, that is the least likely problem and would require removal of the gas piston to cure. I don't recommend doing this unless as a last resort.

Quote:

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Originally Posted by jimb16

There could be a partial blockage of the gas port.

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Not very likely since it also happens when he pulls the op slide back manually.

The sear feels rough? Maybe someone tried to lighten trigger pull with a stone and went through the hard facing and the sear is now being chewed up? If you look at some later carbines (Winchester?) you will see a very noticeable section on the sear that is polished at the factory. Early ones not so much. The first thing I'd do is take out the Wolf springs and put them away, get a new sear and change the sear spring to a GI spring. Perhaps someone got a bag of Wolf springs and put the wrong one in the sear? There are no instructions with the Wolf spring assortments.

Seen on the Video that when the Hammer is full forward that the left edge of the Hammer stop isn't resting on top of the left rail of the Trigger Housing..... Small gap between.
Only reason I could think would be:

The Upward push on the bottom of the Hammer by the Sear. If the Pin hole on the Hammer is reamed out..... It may be causing this. Easy enough to check if your going to be looking at the Sear. Also look for extra play.... like side to side wobble with the Pin thru the Hammer. With and Without the Hammer spring and it's Strut installed.

Maybe not it, but worth a look while your in there.

**** Where do you live? ****

Quote:

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Originally Posted by W5USMC

Not very likely since it also happens when he pulls the op slide back manually.

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True....but it is a remote possibility also barrel alignment could be off causing drag od the slide, but again that is another very remote possibility. I've worked on enough carbines to not discount almost anything. To me the most likely suspects are the trigger spring, sear spring and sear faces on both the hammer and sear. The only other thing that I can think of is a misaligned hammer pin or sear pin hole in the trigger housing, but that is another far fetched possibility. But, I have seen that once!

Well - took things back apart and tried turning the sear spring around to no avail. So, I put in an order for a new hammer, sear, and trigger spring.

I'll replace those one at a time when the parts come in and see how it goes.

Thanks again all!

Unlike the M1 rifle, the carbine sear and hammer can be oiled. I'd try that. That hammer spring is a powerful spring. Carbines are weird: My NPM fresh from CPM had a time when it was not moving the slide far enough to eject and cock the hammer, logic says that it was too strong on the slide spring or too weak on the piston. I replaced the spring with a new GI one and the problem went away.

Hi there I was referred to your posts from a different forum. I posted the same exact question and almost identical video that you did. My carbine is doing the same exact thing yours did. Were you able to fix it, was there any one specific cause if so

Quote:

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Originally Posted by mmr61184

My carbine is doing the same exact thing yours did.

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Except, Your Trigger Spring has a broken leg.
New Spring you'll be good to go.

See this Video and compare the movement of your Sear:

https://www.milsurps.com/showthread.php?t=17368

I just got a package in today with a new hammer, sear, and trigger spring.

I replaced the hammer first and nope - didn't fix the issue.

Swapped back to the original hammer and replaced the sear next. BINGO!

Works flawlessly now.

Thanks all for your help in diagnosing this!

Quote:

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Originally Posted by Pacifist86

I just got a package in today with a new hammer, sear, and trigger spring.

I replaced the hammer first and nope - didn't fix the issue.

Swapped back to the original hammer and replaced the sear next. BINGO!

Works flawlessly now.

Thanks all for your help in diagnosing this!

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Congrats!!