M1 Carbine Gas Piston

[CrazyIvan]

Hi Everyone,

I have a NPM M1 Carbine with Underwood barrel. She's mostly a mix-master, but in good condition. I've been having problems with the gun failing to eject (spent rounds extract just fine) and it also regularly fails to feed as well. Most of the time, the bolt either stops at the round and fails to push it from the magazine or the round slides forward and jams at an angle. I've tried multiple magazines and even magazines that have worked well on other GI issue carbines. The overall failure rate is 2 or 3 times per 15 round GI magazine.

One thing I noticed was that there seems to be some blowby at the gas piston, with heavy carbon build-up where the piston contacts the operating slide. The piston moves extremely easily so that isn't a problem. Is this blowby normal? Could this be the cause of my problems?

On another note, I noticed that the barrel does have the flaming bomb below the date of manufacture but no proof P on the barrel. Does this mean the barrel was replaced at some point. It is the right barrel date for the serial # on the receiver. (I'm just curious about this.)

Any help would be greatly appreciated.

Cheers,
CrazyIvan

 

[danbtech]

NPM did not use a P proof mark,look for a punch mark on the top of the barrel.

 

[CrazyIvan]

Thanks Danbtech! The barrel does have the punch mark.

Happy Independence Day!
Crazy Ivan

 

[Oldcarjunkie]

In for info, my buddy Has a Carbine that does something very similar( jamming on known good mags)

 

[CrazyIvan]

NRA offers advanced maintenance classes for he garand but not the carbine. I would love to take an advanced course in rebuilding these rifles. They are really fun to collect.

 

[Oldcarjunkie]

We took his apart side by side with two of mine and couldnt find anything that looked out of the ordinary. Even had it feeding here at the house with no issues. got back to the range and wham.. no workie.

 

[obsolete]

I had one about fifteen years ago that malfunctioned like you are describing. A new recoil spring did the trick for me. I think the weak spring allowed it to unlock while the pressure was still a little high and then didn't have enough umph on the return stroke.

 

[airsporter]

I had one about fifteen years ago that malfunctioned like you are describing. A new recoil spring did the trick for me. I think the weak spring allowed it to unlock while the pressure was still a little high and then didn't have enough umph on the return stroke.

That would be my first attempt to solve your M1's problem.

http://www.fulton-armory.com/recoilspringnewgi.aspx

http://www.gunsprings.com/index.cfm?page=items&cID=2&mID=98#534

Worst case, it doesn't work and you have a spare mainspring. Wolff spring is a little higher but they only charge $4 for shipping vs. Fulton charging $10 for shipping + Md tax.

 

[CrazyIvan]

Thanks for the links!

Well, I checked the gas tube to see if it was clogged (My gas nut wrench arrived via ups before the new wolfe springs I just ordered) and the tube was open. I used a straitened paperclip and it went smoothly into the barrel through the gas tube with no carbon or debris left behind. I cleaned the piston and nut and reassembled them. I'll try out the new springs next time I go to the range and see if that helps.

I forget where I read it (might have been a thread on here) that sometimes the Wolfe springs are too heavy, and may need to have coils removed to give proper operation. How would I know the difference between a "too heavy" spring making it not cycle properly vs. a "too light" spring not making it cycle properly?

 

[airsporter]

Too heavy and you may have failure to eject, failure to cock hammer, and/or the bolt will go back to battery without picking up a round from the mag (may even jamb the fired casing). Too light is probably what you have now.

 

[CrazyIvan]

Thanks everyone for all of your input and advice! I just received the new Wolfe springs today so I'm going to take the carbine to the range this weekend and see how it does.

Cheers!
Crazy Ivan

 

[toolness1]

I had similar jams as you described, where it would start to feed but jam the round at an angle.

I ended up changing to a Wolff extra power recoil spring, and also put an M2 magazine catch on (holds the mags a bit more stable) and it solved the problem for me.

I did both things at the same time so not sure which one fixed it, or if it was a combination of the two... My mags did seem a little wobbly before, that's why we thought to try the M2 catch, which was made for holding the 30 rounders.

Good luck!!

 

[CrazyIvan]

Hi Everyone,

I removed the gas piston and nut, cleaned out the gas tube (it was clear) put it back together and replaced the oprod spring with a new one. The new spring was about 1/2" longer than the old one, so I guess the old spring was rather compressed.

Well, a trip to the range and it's worse than before. I couldn't get more than one round out of the gun. Though I inspected the bolt and everything seems ok, I am now going to replace the ejector, extractor and their corresponding springs to see if this helps.

I'm also wondering if the magazine is sitting just a little too low in the mag well. This carbine was refurbished at some point and has a M2 trigger group and magazine catch already installed.

Today at the range, I was noticing that the spent cartridge casings were extracted clear of the barrel and left laying on top of the new cartridges in the magazine. When I tested her at the house before going to the range, i could manually cycle the carbine fine with the same box of cartridges I took with me to the range.

When the carbine failed to feed, I noticed that the bolt was (in most instances) sliding part way over the new cartridge before catching and partially stripping the cartridges from the magazine, jamming the bolt.

I'm already approaching the end of my technical expertise with this thing. I'm typically good at "intuitive tinkering" and fixing things myself, but this really has me stumped. Does anyone know a good gunsmith local to the Columbia area that you would trust with your significant others favorite rifle? Is it worth sending it to Fulton armory since they specialize in Carbines and Garands?

 

[toolness1]

Damn, sorry to hear you're still having problems. Good luck and keep us updated with what you find out!

 

[airsporter]

Out of curiosity, what ammo are you using? Have you tried any other?

 

[CrazyIvan]

Hi, I have tried Winchester White Box, Aguila (both brass cased) and Hornady steel case match ammo. All performed the same. I also used two different new 10 round magazine and a new old stock 15 round GI magazine.

 

[airsporter]

I don't think Fulton takes walk-ins but its worth a call. Unfortunately, they charge like $80 to inspect + cost of work/parts/return postage.

 

[Drmsparks]

broken carbine fixer

have you tried this guy?

 

[CrazyIvan]

Thanks!

I'll give this guy a call tomorrow.

I read the thread and forgot he gave a name/number.

 

[CrazyIvan]

Thanks!

I'll give this guy a call tomorrow.

I read the thread and forgot he gave a name/number.