why did my M1 carbine keep jamming when i used the 30 round mags?


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rod5591
February 18, 2012, 08:35 PM
I took my .30 m1 carbine to the range. I had 15 round mags and 30 round mags. the 15 round mags worked fine but the 30s kept jamming ever few rounds. Anyone know what might be wrong?

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rcmodel
February 18, 2012, 08:37 PM
You didn't have real GI surplus 30-round mags, would be my first guess.

A lot of the after-market carbine mags are crap.

rc

dafitch
February 18, 2012, 08:45 PM
Do you have the correct magazine catch? 30 rd magazines need type 4 catches to work correctly. As for magazines- the 30 rd Korean versions work perfectly for me with the type 4 catch.

jeepnik
February 18, 2012, 08:48 PM
Yep, I'd go with bad magazines. Stick with GI mags and you'll likely not have any problems. Besides, push comes to shove, two 15 round mags that work are far and away better than one 30 that doesn't.

USSR
February 18, 2012, 09:00 PM
rcmodel is correct; commercially made 30 round mags are crap, use USGI 30 rounders. The mag catch is not likely the problem. I run 30 round mags all the time without a M2 mag catch.

Don

Onmilo
February 18, 2012, 09:00 PM
I agree with dafitch
If you don't have the type 4 magazine catch with the offside support tab, the heavier 30 round magazines become mispositioned and rock around a bit which will cause malfunctions.
Catches are available from Bill Ricca and Orion 7 among other places and are an easy retrofit.

Art Eatman
February 18, 2012, 09:56 PM
Sometimes the feed lips aren't righteous, which is easily fixed with some judicious tweaking with needle-nose pliers.

rcmodel
February 18, 2012, 09:59 PM
I run 30 round mags all the time without a M2 mag catch.Me too.

Unless you have an M2 full-auto carbine, the mag catch isn't the problem.

That's why the type-4 catch came about.

rc

amd6547
February 18, 2012, 10:10 PM
Plus 1 on the Korean mags...they worked fine in my Inland with the type one catch. I installed a type four catch just for the heck of it.

greyling22
February 19, 2012, 01:10 AM
I was given 4 old 30rd commercial mags. I can't even load them past 12. the follower binds up. do the korean 30's work? I'd like 1 functional 30.

briansmithwins
February 19, 2012, 07:10 AM
From after action reports I've read, the M1 Carbine was never the most reliable of weapon from the start*. It was rather a rush job and, if i remember 'War Baby' right, they never could make it pass some of the acceptance tests.

But, since they could be made cheaply by manufacturers that couldn't make M1 Garands, they were massively produced anyway.

BSW

*Kinda like the early M16 but w/o the benefit of the additional development work that was done on that rifle.

carbine85
February 19, 2012, 10:38 AM
Quote:
I run 30 round mags all the time without a M2 mag catch.
Me too.

Unless you have an M2 full-auto carbine, the mag catch isn't the problem.

That's why the type-4 catch came about.
I agree with this, however I would add the mag catch to your rifle if don't have one.
From after action reports I've read, the M1 Carbine was never the most reliable of weapon from the start*. It was rather a rush job and, if i remember 'War Baby' right, they never could make it pass some of the acceptance tests.

But, since they could be made cheaply by manufacturers that couldn't make M1 Garands, they were massively produced anyway
The M1 Carbine wasn't really used for it's intended propose. It worked very well for the intended purpose. The problem was it became so popular and in demand that they had to make improvements on the fly.
The M1 Carbine wasn't known as a jam-o-matic until the M2 kits came along, and the mag catch pretty much cleaned that up.

Tommygunn
February 19, 2012, 12:53 PM
There are newer Korean 30 rounders that are pretty good mags, but as stated, older commercial ones are .... questionable.
The M-2 catch with its extra "finger" is a necessity. I found that out on my Inland. Once I put that catch on (an easy as pie fix) my carbine ran fine with 30 rounders.
Another problem might be magazine lips, or if you use soft nose rounds. Tweaking the mag lips has already been discussed. The carbine was developed to use ball ammo -- what we call FMJ. Some carbines have problems with softnose and hollowpoint rounds.

I think most of the possibilities have been covered. Giving us a better idea of exactly what was happening, even pictures if possible, always helps.

SHR970
February 19, 2012, 01:27 PM
On my GI 30 carbine I ran into the same problem when running a hollow point load and it didn't matter what 30 round mags I was using. I replaced one part and the problem went away. I replaced the Mag Catch to the M2 style aka type 4. The 30 round magazine came about because of the M2. Change this one part and you should only see issues with the more sloppy of commercial mags.

What you need (http://www.fulton-armory.com/magazinecatchm2.aspx)

Husker_Fan
February 19, 2012, 02:36 PM
The CMP has a great PDF on 30 rounders. Mine are all AYP stamped. These were made by FN for NATO contracts after the war. They work flawlessly and are the only non-GI mags of older vintage that do. The currently available mags from Korea are also very good.

As for the catch, I run a type 3 with 30 rounders. I think the added support of the type 4 is good if you are putting a lot of torque on the magazine by banging it around in the jungles of SE Asia. Otherwise, for run of the mill range and HD duty, I don't think it's necessary.

Husker_Fan
February 19, 2012, 02:38 PM
On my GI 30 carbine I ran into the same problem when running a hollow point load and it didn't matter what 30 round mags I was using. I replaced one part and the problem went away. I replaced the Mag Catch to the M2 style aka type 4. The 30 round magazine came about because of the M2. Change this one part and you should only see issues with the more sloppy of commercial mags.

That's interesting. I have some HP bullets that I have not loaded up yet. I'll be interested to see how they work, and if they don't, I'll get a new catch. The SPs I've used work fine, but they all have a profile nearly identical to the FMJ.

bigfatdave
February 19, 2012, 02:55 PM
Perhaps it would help to know what version of the M1 carbine the OP has ... and what ammo/magazine is being used

Based on this thread (http://www.thehighroad.org/showthread.php?p=7971849) I'm taking everything with a grain of salt, rod5591 appears to be very new to maintenance and troubleshooting on firearms.

And "jamming" doesn't begin to describe the malfunctions, were the rounds going nose-up or nose-down while feeding? Was it just not quite making it back to battery? Is there some other underlying problem? Is the magazine garbage? (I've been burned by crap magazines, it happens and you move on) Is the ammo underpowered? Is the gas system in good repair and clean? Is the carbine a CMP rebuild, a good commercial model, a bad commercial model, or a war relic?

1KPerDay
February 19, 2012, 04:00 PM
The Korean 30 rounders have been flawless for me with and without the M2 mag catch. More reliable than my GI 15 rounders, actually.

ball3006
February 19, 2012, 04:00 PM
You answered your own question with your post. It is the magazine. If your rifle operates just fine with 15 round mags, why fool around with 30 round mags that don't work? chris3

zeke
February 19, 2012, 04:34 PM
"The M-2 catch with its extra "finger" is a necessity. I found that out on my Inland. Once I put that catch on (an easy as pie fix) my carbine ran fine with 30 rounders."

ditto, and the 30 round Koreans are close to the old military versions.

Nicky Santoro
February 19, 2012, 06:54 PM
OP,
Even the old genuine USGI 30 round mags were never as reliable as the 15s. Unless your 30s are true USGI or even Korean you'll likely find them problematical.

Art Eatman
February 20, 2012, 12:49 AM
In the way back when, I'd occasionally liberate a 600-round can of ammo and go down to the beach at Inchon and harass seagulls with my M2. All we had were the 30-round mags. Everything always worked.

My father's bring-back M1 works okay, 15s or 30s.

rod5591
February 20, 2012, 02:12 AM
Perhaps it would help to know what version of the M1 carbine the OP has ... and what ammo/magazine is being used

Based on this thread (http://www.thehighroad.org/showthread.php?p=7971849) I'm taking everything with a grain of salt, rod5591 appears to be very new to maintenance and troubleshooting on firearms.

And "jamming" doesn't begin to describe the malfunctions, were the rounds going nose-up or nose-down while feeding? Was it just not quite making it back to battery? Is there some other underlying problem? Is the magazine garbage? (I've been burned by crap magazines, it happens and you move on) Is the ammo underpowered? Is the gas system in good repair and clean? Is the carbine a CMP rebuild, a good commercial model, a bad commercial model, or a war relic?

the jams were nose up. the ammo was Remington 110 gr UMC. the mags were made in USA. see pics. I dont know what catch it has. I took some pics. I have a 1944 Underwood.

briansmithwins
February 20, 2012, 05:22 AM
Not to sound like a D bag, but that carbine might work better if you clean the old, dried out cosmoline off of it.

BSW

Husker_Fan
February 20, 2012, 08:51 AM
The rifle has the M2 mag catch. What do you mean by the mags were "made in USA?" What markings are on them.

MJD
February 20, 2012, 09:01 AM
You might try the 30 round magazines available from Cheaper Than Dirt. They run the best of any 30 rounder I've tried; I have had no trouble with them.

I'd also recommend giving that carbine a good cleaning inside and out.

Enjoy your carbine.

Art Eatman
February 20, 2012, 11:05 AM
If the jams were nose-up, that sounds like the feed lips need to be bent in just a tad. While I've not had feeding problems with a carbine, I've fixed many a 1911 magazine in that manner.

bigfatdave
February 20, 2012, 10:45 PM
the jams were nose up. the ammo was Remington 110 gr UMC. the mags were made in USA. see pics. I don't know what catch it has. I took some pics. I have a 1944 Underwood.
I've had Rem .30carbine ammo work, but it does seem a tad less powerful than the Aguila and Lake City I get from the CMP, or the PPU soft points I keep on-hand.

Nose-up seems to imply early release from the feed lips, I'd suggest comparing to the lips on a known good magazine, someone here might be able to give you pointers on how to tweak them and/or what tools to use (I will leave that to an expert, I'd experiment on my magazines, but won't tell you how to experiment on yours ... know-what-I-mean?)
I also can't casually ID magazines, but those look beat-up enough to be GI ... were they coated in a waxy oily mung when you got them?

The cosmoline comment yields a thought: perhaps your mags are gummed up inside with preservative? Disassemble if possible and clean them out, look for irregularities, and leave them oil-free, lube with a dry product like "Liquid Wrench" if needed.
And yes, removing some of that cosmoline might help your magazines seat properly.





*liquid wrench makes a great dry-lube, looks like this: http://www.liquidwrench.com/assets/img/products/dry-lubricant.png
look at the auto parts store, the gun-specific version is expensive and it is a LOT cheaper to buy in a shop compared to ordering online anywhere I've seen it

Husker_Fan
February 21, 2012, 10:09 AM
Nose up could also be caused by an exceedingly dirty gun or worn spring causing the slide to move too slow.

rod5591
March 1, 2012, 10:11 PM
The rifle has the M2 mag catch. What do you mean by the mags were "made in USA?" What markings are on them.

"Made in USA" is stamped on the narrow side up close to where the bullets go into the mag.

rod5591
March 1, 2012, 10:13 PM
thanks for all the advice!

rod5591
March 12, 2012, 08:59 PM
Not to sound like a D bag, but that carbine might work better if you clean the old, dried out cosmoline off of it.

BSW
how would I go about doing that? Cleaning the cosmoline out?

rod5591
March 12, 2012, 09:11 PM
Based on this thread (http://www.thehighroad.org/showthread.php?p=7971849) I'm taking everything with a grain of salt, rod5591 appears to be very new to maintenance and troubleshooting on firearms.

yes you are correct Sir that's why I am on line at this forum seeking the advice of experts such as yourself.

briansmithwins
March 12, 2012, 09:39 PM
I'd use either diesel fuel or hot soapy water to clean all the old, dried cosomoline out.

Diesel oil smells worse but can't cause rust like left behind water can. Pretty much tear it down as far as possible and go to town with solvent and a brush.

Have fun.

BSW

Orlando
March 12, 2012, 09:52 PM
He has commercial mags, thats the problem

SharpsDressedMan
March 12, 2012, 10:41 PM
I have two GI carbines, both updated with the M2 mag catch, and ALL 30 round mags I have tried work well. I particularly think the newer Korean made ones are the best. Most true GI 30 rounders are a bit worn and springs may be weak.

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