M1 Carbine Jam

A couple of months ago, my wife and I borrowed my father's M1 Carbine to shoot in the Monumental RPC match. After a couple of sighters, she started shooting for score and began having jams like this:

I wish I had taken the time to get a better picture...but...oh well At least it's something...

We were using cheap imported mags that were known to be finicky. Since we wanted to both shoot for score before the next cease fire, we just soldiered through. I'd say out of 60rnds total between us, we probably had 7ish jams. At first, she was kicking the jammed round out and rechambering. I found I could just pull the bolt back a little and let it drive the offending round in.

After the match, I tried a known to be reliable mag, to ease my mind...and it did the same thing. Uh-oh! I had Dad's whole box of M1 stuff, so I tried several combinations of three "good" mags and three types of ammo (one being the milsurp ammo that this carbine has been fed for my entire life, new PPU and new Rem). Every combination would jam at some point...not every round, and not always at the beginning or end of the magazine, but always in the same fashion.

The rifle was (or started out) clean and well lubricated. Nothing has been done to it recently (heck, it's just been resting since the Carbine match the year before, when it worked fine).

The gas piston has not been staked in. When I took it apart to clean it, the nut was loose, but only by about 1/8 turn from being finger tight (last year, I'm sure I tightened it with the appropriate wrench before it went into hibernation). In the past, I'm pretty sure it has been looser and still worked. Neither the piston nor the nut appeared damaged, worn, or excessively dirty. I don't think this is the problem. At some point, I do want to stake it. I believe this is done with a brass rod "beaten" into the hole of the gas chamber?

So what says the braintrust? Stake the piston? (yeah...yeah...it's been waiting 40+ years for that, but we'll get to it eventually). Springs?

Light ammo? I have had light ejection with Aguila ammo before.

M1s are usually ultra reliable in moderate temperatures as long as everything is clean. I have 7 of them and can only recount one jam and it was on a no name 30rd mag. are there any burs on the feedramp?

Ill be curious what the issue is.

Jimbob2.0 said:

Light ammo? I have had light ejection with Aguila ammo before.

M1s are usually ultra reliable in moderate temperatures as long as everything is clean. I have 7 of them and can only recount one jam and it was on a no name 30rd mag. are there any burs on the feedramp?

Ill be curious what the issue is.

Click to expand...

This one had also been ultra reliable. It's been part of the family longer than I have (which is 38 years), and the only issues I've ever known it to have were from...you guessed it, cheap mags.

The ammo was all factory FMJ, new made Rem, new PPU, and...whatever surplus my dad had (which the rifle has been digesting just fine for...probably 40 years). No reloads, or lead bullets or anything weird. None of the troublesome rounds seemed any lighter than usual. It seemed to eject ok...(I wish I had posted this sooner when it was fresh in my mind!) Most of them were going about an AGC lane width (5ft, I think?) or two over. Some did go more forward as I definitely remember hunting for brass in the grass. Certainly not Mini-14 trajectories, but they weren't just dribbling out at my feet.

Because of the variety of ammo and mags I tried, I really think it has to be something with the rifle. The bolt was well lubed with synthetic grease (Shooter's Choice, I think). It was cold out, but i don't think cold enough to cause a problem.

I don't have access to the rifle right now. I should be able to get ahold of it this weekend and look for burs. Nothing stood out to me when I cleaned it, although I was admittedly more focused on the gas system.

My dad thought perhaps the spring (which google tells me is technically called the "operating slide spring") may be getting weak and not pushing the bolt closed hard enough. As far as I know, he hasn't changed any parts on the rifle since he bought it in the 60's (?)...so this sounds like a definite possibility to me. It can't hurt to put a new spring in, right?

Make sure the feed ramp is clean and does not have a burr on it. Switch out the slide spring. Double check the mag lips to insure that they are not bent or contain a burr. Check the tension of every mag spring to insure that all the rounds are under adequate tension/pressure as each is being released from the magazine. Good luck with the shooting, too.

Saw my very first M1 Carbine in Nha Trang in 1966, carried one on each flight I made for Det D, 1s MI Bn (ARS) and never left NT without it. Never had to use it, never test fired it and started collecting the little guns in 2002. Own one each of the ten prime manufacturers. Great little rifles they are!

Lew--Ranger63
Korea, Vietnam (2), Germany

Most M1 carbine feed issues are mag related. Have you tried a know good 1?

My Carbine recently started doing the same thing. I was shooting reloads but I had never had a problem before with them. It had the same issue with all three of my mags (non USGI). I too came to the conclusion that it was a bad slide spring as that is the only thing left that made sense. I have not yet tried a new spring but plan to.

I tried two known to be good mags, same result. I'll look closely at the feed ramp this weekend. I'll double check the mags, but I don't think the good ones have been dropped or damaged. I figure I should be able to find a slide spring at the HoCo show this weekend, just not sure when I'll get to test it out.

Don't you hate it when someone posts a thread like this, and never follows up? Me too...but there's not a whole lot to follow up one yet

I haven't managed to get to the rifle to check the feed ramps (possibly this week), but I did pick up a spring ($8 from E.C. Depot at the HoCo show). For that price, it certainly can't hurt anything to try...if I ever get back to the range

That looks like a bolt over base misfeed (round fed by the bolt pushing on the extractor groove). Is that what actually occured? If so the bolt may not be pushed back enough (friction or gas pressure/volume) or the mag springs are weak and not pushing the round up fast enough. That is where I would start.

Rack the action all the way back. Does it feed a cartridge into battery? If so I would disassemble the rifle and inspect the gas hole that operates the slide. Check the piston and make sure that it is clean and serviceable.

I put the new spring in Friday before going to the range. Before and after pulling on the bolt with my completely subjective and uncalibrated trigger pull gauge (i.e. booger hook), it felt like the new spring was a little tighter...maybe

At the range, after about 40+ rounds of various ammo in a variety of mags (including a couple known to be suspect ones) and no malfunctions whatsoever, we seem to be all better

Good to know !!!