M1 Carbine jamming

I have a Standard Products M1 carbine that has been jamming since I bought it. I have tried clean, dirty, oil, no oil, grease, no grease, GI an Korean mags and it still jams. Last time I shot it it worked perfectly. I cleaned it, heavily oiled it, and installed a new GI recoil spring and it was fine. A couple days ago I shot it and it jams twice per magazine again. Ammo is American Eagle. If you watch somebody else shoot it from the side the action is not cycled consistently. Sometimes it barely goes back enough to eject the empty, sometimes it goes all the way back. It is ejecting brass in all directions and when it jams it is catching the empties length wise between the bolt and receiver, case mouth facing forward. I have chronographed the ammo and it is full power and consistent. The empty brass is also covered in soot more heavily than any other gun I have fired. The piston moves fine and the piston nut is tight. Anything else I need to look at.

Rebuild the bolt.

I was going to say clean the piston but you are saying it moves freely. Have you checked the ejector and extractor?

You might want to try different brands of ammo. American Eagle isn't particularly hot ammo and I've noticed with my new AO that my lightly loaded handloads sometimes cause failures to feed where my full charge handloads cycle just fine. The light stuff works fine in my original '43 NPM carbine as do my soft point handloads but my new AO seems to fancy only the warm to hot loaded ball ammo.

Do the most obvious first:
Scrub/clean the chamber. Used cleaner and a brush followed by patches
Different ammo
Different magazine

If cases are heavily sooted, as you say, that seems to indicate insufficient chamber pressure to obdurate the case.
I.e. the case isn't expanding all the way to the chamber walls and sealing properly.
Up front: I'm no expert on ballistics and powders, but if you're getting sooted cases and full-power velocity readings (which IIRC are around 1950-2000fps with ball ammo), that sounds like there's something weird happening with the powder.

Unfortunately for my hypothesis, I can't come up with an explanation for how both of these things would happen.

Check different ammo, is all I can come up with, if you've checked the recoil spring and overhauled your mags.
Hammer spring might be worth a look, too, and while you're at it you might as well replace the bolt springs too (extractor and ejector, IIRC).

But I find it hard to believe that you'd be getting full-power, consistent velocity from ammo that only sometimes is cycling the bolt hard enough to pick up the next round, and is not high-pressure enough to seal the case mouth to the chamber walls.

Might be that your chamber is pitted, though, and there's enough gas leakage to not power the piston...but I would imagine (though I don't know for sure) if that's happening, then you also would be getting inconsistent velocity.

so, what kind of velocity readings are you getting from this ammo?

It is common for the 30 carbine to have sooty cases

I chrongraphed 1 15 round magazine and it was 1960- 1970 fps. I see your point about the inconsistent cycling though. Maybe I will chrono again and see if the jams are limp rounds.I am about out of the AE ammo and plan to reload. How tough is it to tear the bolt down without the tool?

Sure is. Makes finding them on the ground a bitch too.


Doesn't sound like the ammo then. Sounds like you're having the same problem with all your mags so you might give a look at your feed ramp for burs or sharp edges. Also look at how the mags position in the magwell. Are they level or is one end tipped up or down?

How tough is it to tear the bolt down without the tool?

DON'T.
While it's possible to disassemble and reassemble the bolt without a bolt tool, you'll be one sorry man you didn't get the tool and the kids and neighbors will hear words they never heard before.

While the Carbine bolt looks just like a miniature M1 Rifle bolt the extractor assembly is different.
In the M1 Rifle the extractor is simply pushed out during disassembly.
Try that with the Carbine and you destroy the ejector and it's plunger.

Like "Jack, pay the two dollars" this is "Jack, buy the bolt tool".

Here's a link to a site that has a lot of manuals including the USGI Ordnance manuals on the Carbine.
These show exactly how to properly disassemble the bolt and the proper way to use the bolt tool. Use it wrong and the pawl snaps off and the tool is ruined.

NOTE the info near the top of the page on what password and user name to use to get access:

http://www.biggerhammer.net/manuals/

Huh. Guess I just learned something about the Carbine, then

Thanks.

humm.... if it was me I would give the gas system a cleaning (think you need a special wrench to open it up) I also would clean the whole rifle well, to included the chamber. I don't think it's the problem but better to start with a clean slate.

I think the problem is coming from your bolt, it sounds like the round is not getting fully ejected. With the M1 carbine, and the M1 rifle, the cartridge is kept under spring tension and you should be able to eject the round just by slowing pulling the bolt to the rear, let alone under full speed from cycling. If you do it slowly and it cant even get out of its own way, I would say rebuild the bolt. Sounds like you shoot the old girl a lot, might have a broken or worn a spring. Then after that's done, shoot the old girl some more.

my .02, Good luck

I have read, and my experience backs it up, that the 15 round M1 mags work much better than the 30 round curved M2 mags.

I've always been told the gas piston setup is designed to be self cleansing... if you take that nut out you'll have to stake it in when you put it back in... or use some locktight.

If nut is staked in place do not try and remove it. Its possible that you will not get it back on, dont ask me how I know.
Piston is basically self cleaning, thats wht the nut was staked on later carbines and does not need to be removed

I agree, however, I recently got a couple of the Korean Mil-Spec 30rd mags from AIM and they work superb; not a jam in a few hundred rounds. HOWEVER, you need the correct mag catch for the 30rd mags. It's got a 'tail' on the side to grab the protrusion on the side of the 30rd mag and hold it in place.

Old style mag catch for 15rd mags only:



Newer style mag catch with 'tail' for both 15rd and 30rd mags:



If you have the old style and want the new one you can buy them most places that sell M1 Carbine parts. Swapping them out is easy too.

I'll have to look my 2 Inlands over and see which they have a look at replacing them if necessary.

Thanks for the info.

Copyright © 1996 - 2013 :: AR15.Com LLC :: All Rights Reserved.
Any use of this content without express written consent is prohibited.