M1A1 "Hiccup" Fire Problem

[Raven Jeff]

I had the same problem with my M1-A1. It is also 1943 ish vintage. Mine was finally resolved by replacing the sear, the rocker and one other small part.

 

Good luck and have fun!

 

Jeff

[hyperdyne]

Jeff, thanks for the info. I tried what TSMGguy recommended and I can hear the click when letting go of the trigger in single (the disconnect popping the rocker back up). It all seems good when checking it out.

 

Anyway, also watched the AGI vid and learns lots. The sear spring seems pretty strong, but I am wondering if my bolt is worn on the sear catch or the sear is worn down too much. Will change out the sear and rocker just for good measure and replace the springs.

 

If I wanted to get an extra M1A1 bolt does anyone have a source? I havent been able to find one yet...

[winbar]

Hyperdyne,

I've been saving my spare parts for the final conflict. Email me direct at Balmrc49@aol.com if you haven't found one in the next few days (try gunbroker). Mine came from IMA a few years back.

Doug

[jim c 351]

Jeff, thanks for the info. I tried what TSMGguy recommended and I can hear the click when letting go of the trigger in single (the disconnect popping the rocker back up). It all seems good when checking it out.

 

Anyway, also watched the AGI vid and learns lots. The sear spring seems pretty strong, but I am wondering if my bolt is worn on the sear catch or the sear is worn down too much. Will change out the sear and rocker just for good measure and replace the springs.

 

If I wanted to get an extra M1A1 bolt does anyone have a source? I havent been able to find one yet...

 

Hyper,

A friend of mine has 2 new in wrap M1A1 bolts for $75.00 each.

Send me a email if interested.

Jim C

[hyperdyne]

Jim C, yes I am interested. I've exhausted my search already. I have sent you a PM.

 

winbar, thanks! If I cannot acquire one I will certainly contact you. Much appreciated!

 

Regards,

Jim S.

Edited April 6, 2012 by hyperdyne

[winbar]

Jump on that offer, if I didn't already have mine,I'd be begging for them.

Doug

[hyperdyne]

So I was able to get a bolt (thanks Jim) and changed it out with a surplus sear. Also put in new springs for the whole trigger pack. As I was looking at some of the surplus parts, I see that the trip I have is shaped a bit differently than the trip I purchased. I am not sure if the surplus trip was GI spec. Also, the flat side of the surplus disconnector (that sticks up and blocks the sear lever) I bought was also a tad wider than my stock one. Not sure if that even matters. The rocker I have looks sharp and in good shape so I kept it in.

 

After reassembly the test functioning passes. I am puzzled on the slight differences in the parts but will test fire and see if the issue is solved.

 

Thanks!

 

-----

 

Well, after looking in american thunder ii I answered my own question. The surplus trip I have is a 1928A1 version. The original m1a1 slopes off a bit more. But it appears they are interchangeable.

Edited April 22, 2012 by hyperdyne

[hyperdyne]

The other question is whether I should keep the Wolff extra duty spring or replace it with a surplus GI recoil spring. Anyone have thoughts there?

[darrylta]

I'd keep the Wolff recoil spring and get some HD XXX Wolff mag springs as well.

I trim the the GI XXX springs a bit and put them in my XX mags also.

I hope your redue solves the problem.

Be safe,

-Darryl

[hyperdyne]

Well looks like I am back to square one. Went and fired the thompson after the changes and it acted worse. Double and tripled up in full auto. I even had it run away in single. I have no idea. I changed all the springs in the trigger group other than the trigger spring. The original is actually a tad longer than the surplus trigger spring I bought, wasnt sure why.

 

Anyway, I guess I will swap out more parts until I figure it out. It doesnt appear to be the sear or bolt as I replaced both. I wonder if the wolff spring is too stiff.

[jim c 351]

Well looks like I am back to square one. Went and fired the thompson after the changes and it acted worse. Double and tripled up in full auto. I even had it run away in single. I have no idea. I changed all the springs in the trigger group other than the trigger spring. The original is actually a tad longer than the surplus trigger spring I bought, wasnt sure why.

 

Anyway, I guess I will swap out more parts until I figure it out. It doesnt appear to be the sear or bolt as I replaced both. I wonder if the wolff spring is too stiff.

 

hyper,

If you would care to mention your city and state, maybe one of the members near you could have a look at your M1.

Jim C

[hyperdyne]

Sure I am located in Superior, Colorado - its near Boulder.

[jim c 351]

Sure I am located in Superior, Colorado - its near Boulder.

 

hyper,

OK,-now hopefully someone will step forward and have a look at your M1.

As far as the Wolfe bolt spring is concerned , I'd take it out. The Wolfe springs are usually stronger that the military and with underpowered ammo could prevent the bolt from reaching the first bolt notch, but comming back far enough to pick up a cartridge..Best of luck.

Jim C

[darrylta]

Hyper,

Check to see if the rocker is in right. The hook should be

facing the rear of the gun.

I have Wolff springs in all my Thompsons, haven't had any problems?

-Darryl

[hyperdyne]

Yeah the rocker is in right. I double checked that. It fired fine in semi auto the first several times. After a full auto burp I went back to single and the issues cropped up.

 

I am going to go back to a GI spring for now and also replace the disconnector and trigger spring. Those were the only other pieces that looked suspect to me.

[TD.]

There is a gunsmith from Delta, Colorado listed in the FAQ section at the top of the Thompson Forum. His name is Paul Krogh; he is known as PK. on the Board. If in the end the parts swapping does not work to your satisfaction, I suggest you give him a call and discuss your problem. I know he can figure out what is wrong and fix it. Looking at a map his shop appears to be about a 5 hour drive from Superior, CO. It may seem like a long drive, however, I wish Paul lived in my state!

 

Keep us informed on your progress.

[jim c 351]

Hyper,

One other thought crossed my mind. Have you let anyone else shoot the gun. Did it malfunction for them.

Reason I ask, if you have some unique way of manipulating the trigger, whereby you think you are releasing the trigger all the way , but you aren't, well that could be a problem.

Here are 2 examples that happened to me.

 

#1.-In the late 70s , I was at Camp Perry shooting a DCM match run by Ohio Rifle and Pistol Asso. In those days the DCM provided LC Match ammo. I was shooting a H&R M1 rifle and my partner was shooting a NM M1 rifle. All went well in the 200 yd slow fire stage, but when firing the 200 yd rapid fire, my partners rifle fired a 3 rd burst. The range officer got involved and allowed a refire. Another 3rd burst resulted.

At this point I offered my rifle. The range officer allowed another refire. I had my rifle for almost 20 years and it never once malfunctioned in any way. Well when he pulled the trigger, another 3 rd burst.

As near as we could guess, it was trigger manipulation. My partner was a serious pistol shooter who had borrowed the M1 to shoot the match. Instead of pulling the trigger straight back, he was pulling it ever so slowly that the sear hung at a critical point and the recoil did the rest. There was nothing wrong with either rifle.

 

#2. When my Group Uzi is set on semi and I pull the trigger ever so slowly it will fire a double. If I pull straight thru this doesn't happen. I think its just the design of the gun.

 

Just something to think about and further confuse you.

Jim C

[hyperdyne]

Jim,

 

Good food for thought. Before I changed out parts it would misbehave for others but somewhat randomly. I will let me buddy fire it now and see what happens. It is in the realm of possibility. The trigger spring gives a pretty long pull, and I thought that may be the issue. If the gun still misbehaves after a couple runs with different people, I will change out the trigger spring with my surplus one. The surplus spring is a bit shorter than the original, and it results in a much shorter trigger stroke when installed.

 

I initially thought the trigger may not be resetting properly, but who knows. When I checked the AGI vid, the spring length in their trigger pack was the same length as my original trigger spring. So I kept it in rather than installing the shorter one. Not to mention the trigger pack in the AGI vid was for a 1928 and not an M1A1. But they should be interchangeable. I'll work on it a bit more.

 

I also looked at the buffer. The original buffer fiber material was really cracked and shrunk. I got a new surplus one and there was a huge difference in thickness of inner material. I just installed the new one, as I wasnt sure if that could be causing excessive bolt slap to make matters worse.

 

Thanks for the feedback.

 

Jim

[hyperdyne]

Jim, I had a similar experience. I received a M1A from my father in law, he outfitted it like he had in vietnam. I had never fired one. The first trip to the range went ok at first, but then I got a double fire. Not knowing what went on it did it again. I packed up my stuff and wasnt going to shoot the rifle again. I then read up on this and saw it was trigger press and how you held the rifle. I too shoot pistols mostly so there is a possibility I am doing something with the trigger to make it unhappy. With that info I may change out the trigger spring so there is less chance of trigger slop.

[hyperdyne]

Ok, I changed some other parts and shot the gun again. Has anyone experienced a heat related issue with the SMG doubling or misbehaving as it heats up?

 

I have 2 data pts now that as the gun heats up things appear to go bad. It may be coincidence, who knows.

 

I changed out the following components after inspecting the originals:

- disconnector

- disconnector spring

- sear lever

- sear lever spring

- sear spring

- bolt

- recoil spring (GI)

- buffer

 

After doing this, the gun fired wonderfully right out of the case. The only issue is the hold open was not working. I am not sure if this may be a mag issue, trip, or the spring itself. But single and auto fire was very good.

 

After this, I wanted to see if the wolff spring was the culprit to the hold open issue, so I changed the recoil spring out for the wolff one. Again, the gun ran wonderfully. You could tell the wolff spring gave a crisper feeling, whereas the GI spring would allow the bolt to slap the buffer pretty hard. And with the wolff spring the hold open was working.

 

After 150 rds or so the gun started doubling/tripling up on auto. I thought the wolff spring was the issue and I was getting lucky. So I went back to the GI spring and the gun ran alittle better and only doubled up a couple times. At this point I was lost. I tried changing the trigger spring out but that didnt help. In fact the gun started running away in semi auto mode. After that I quit to digest all what had gone on.

 

Looking at the bolt underside, the sear is leaving a thin line of scrape marks below the rocker channel. I think the new sear spring is working but now am considering changing the sear out as well.

 

Does anyone have insights or similar experiences they can lend? I am getting confused. BTW, I let my buddy fire it and he had similar issues.

 

Jim

[winbar]

Hyperdyne,

I was waiting to see if an RKI asked about your barrel's condition. I was wondering if the problem appeared only after the gun was"hot". Maybe you are getting gas blow-by as the breech is worn and the gas shoots out of edge of the expanded case and/or the bullet entering the barrel.

Doug

[hyperdyne]

As far as I know the barrel looks ok. To be honest I dont know how many rounds have been through it. The entire gun looks like stock. I can take some pics of it. Is there some telltale sign I should look for?

[winbar]

Jim,

You said you mostly shot pistols. The breech end of the TSMG barrel should ideally look like a brand new .45 automatic barrel. If you don't have a dental inspection mirror(try Walgreens) you can disassemble the M1A1 and view the breech through the buffer pilot hole. The lands and chamber shoulder should be sharp and pronounced(It should look new.)

I looked in my Thompson library(1 book of 5 separate manuals) for a sustained rate of fire, but could not find one. One U.S. Army firing course required 15 rounds,3 rounds per target. One manual also recommended intermittently cleaning the chamber during long firing sessions.

 

I put a SA inc. shorty barrel (non-chromed chamber) on my M-14 and had extraction problems by the time I got to a third 20 round magazine at the old Fourth of July Machine Gun-Beer Fest. (Probably 15 minutes between magazines.)

 

If your barrel looks good, you might consider buying at least 2 more machineguns so you can let your TSMG cool down longer. Expending 150 rounds of ball ammo would be into your 8th 20 round mag or the end of your 5th 30 round mag.

Doug

[hyperdyne]

Hey Doug,

 

Thanks for the feedback. I will take a look at the chamber and barrel and see if anything looks worn. I was on a compressed schedule and was shooting mags to fine tune the tsmg. It was hot, no doubt about it. Just for testing purposes, do you think passing canned compressed air over the barrel to cool it some is ok? Reason I ask is that I could test the theory that temperature is without a doubt causing the issue. Cooling the barrel slighty should return the gun to normal operating conditions. Of course I dont want to subject the barrel to unnecessary thermal shock.

 

If I am exceeding the sustained rate of fire for the tsmg I will certainly adapt to that. I just wasnt familiar with what this gun can handle normally. In the mean time I have kept the new trigger pack, bolt, and recoil spring installed just to reduce the number of variables going on.

[jim c 351]

Hey Doug,

 

Thanks for the feedback. I will take a look at the chamber and barrel and see if anything looks worn. I was on a compressed schedule and was shooting mags to fine tune the tsmg. It was hot, no doubt about it. Just for testing purposes, do you think passing canned compressed air over the barrel to cool it some is ok? Reason I ask is that I could test the theory that temperature is without a doubt causing the issue. Cooling the barrel slighty should return the gun to normal operating conditions. Of course I dont want to subject the barrel to unnecessary thermal shock.

 

If I am exceeding the sustained rate of fire for the tsmg I will certainly adapt to that. I just wasnt familiar with what this gun can handle normally. In the mean time I have kept the new trigger pack, bolt, and recoil spring installed just to reduce the number of variables going on.

 

I would guess that powder fowling would be more of a problem than heat. Unless you got the gun super hot , the bolt and trigger group wouldn't know how much the barrel was suffering..

Jim C