So, M1 Garand goes boom...

[Ownerus]

OK, then what are the mechanics of the failure in your opinion? How does the stock get split into two?

High pressure gas leaking past a failed cartridge case is vented into the magazine well and exposes a large area to pressure. In dealing with pressure, the force is applied over an area. To pull rough numbers out of my head, say the side of the mag well is 2 x 3 inches. That's 6 square inches. Suppose even 5% of the 50k psi in the chamber leaks past the gas seal of of the failed case and pressurizes the volume of the mag well, that's still 2500 psi acting on 6 square inches for 15,000 pound of force....on a thin wood piece. Granted, these are made up numbers but it illustrates what can happen. Sorta like dropping an M80 firecracker into the magazine well and closing the bolt over the top of it.

There's some interesting writing in Hatcher's Notebook about all the development at Springfield Armory to produce brass that didn't do this. Even subtle changes like how a primer was crimped sometimes had major effects.

 

[CLT65]

High pressure gas leaking past a failed cartridge case is vented into the magazine well and exposes a large area to pressure. In dealing with pressure, the force is applied over an area. To pull rough numbers out of my head, say the side of the mag well is 2 x 3 inches. That's 6 square inches. Suppose even 5% of the 50k psi in the chamber leaks past the gas seal of of the failed case and pressurizes the volume of the mag well, that's still 2500 psi acting on 6 square inches for 15,000 pound of force....on a thin wood piece. Granted, these are made up numbers but it illustrates what can happen. Sorta like dropping an M80 firecracker into the magazine well and closing the bolt over the top of it.

There's some interesting writing in Hatcher's Notebook about all the development at Springfield Armory to produce brass that didn't do this. Even subtle changes like how a primer was crimped sometimes had major effects.

I'm confused; how is this any different from what I said?

 

[Ownerus]

As to why M1s and semi-autos in general have less of a safety margin than bolt-actions, I'm not really sure.

Not sure how you reached that conclusion. I'll reference the earlier quote from General Hatcher that was based on actual testing, especially as regards the M1. There may be other reliability issues with a semi auto vs a bolt action simply because there's a lot more going on.

 

[Ownerus]

I'm confused; how is this any different from what I said?

Without re-reading the entire thread, it may not be different. I was specifically addressing the OP's question to my post.

 

[CLT65]

Not sure how you reached that conclusion. I'll reference the earlier quote from General Hatcher that was based on actual testing, especially as regards the M1. There may be other reliability issues with a semi auto vs a bolt action simply because there's a lot more going on.

My statement was specifically in regards to what happened to the OP's rifle. It's common knowledge that there are specifically two types of ammo that you don't want to shoot in an M1:

1. Ammo loaded with too slow of a powder, as the higher port pressure can bend the op rod and slam the receiver.

2. Ammo prone to cracking or rupturing, as semi-autos seem much more prone to being damaged by it, as the OP's was. I've shot questionable old surplus ammo through Turkish Mausers and Mosin Nagants, but I'm much more careful what I shoot in my M1s of FN-49. This is common practice.

 

[Ownerus]

sorry for being Mr. Literal Person but your statement said semi-autos in general.

 

[pathfinder]

Failed case that got stuck in the chamber plus a load little hot for the Garand resulted in an explosive self disassembly of my M1.

Anyone got a replacement stock, preferably USGI one?

Iv got a bm59 set you can look at,

 

[pathfinder]

Failed case that got stuck in the chamber plus a load little hot for the Garand resulted in an explosive self disassembly of my M1.

Anyone got a replacement stock, preferably USGI one?

 

[CLT65]

sorry for being Mr. Literal Person but your statement said semi-autos in general.

You're right, I did. What I had in mind when I wrote that was older battle rifles like the M1 and FN-49, two that I have experience with. Your response addressed the M1, so that's what I thought we were talking about.

I once had a severe case rupture in an FAL, and the rifle survived undamaged. There is this general idea (true or not) that even among modern rifles, a good bolt action is "stronger" than a semi-auto. I'm sure it varies by rifle, but that's wasn't really what I had in mind with my post. Sorry for the confusion.

 

[Ownerus]

I once had a severe case rupture in an FAL, and the rifle survived undamaged.

Any details on the nature of the case rupture? I've had case head separations in both the M1 and FAL where the back half inch of the case ejected and the rest stayed in the chamber. No damage to the rifle in either case. The back of the case still provided a gas seal. I once had a .30 Carbine case head separate through the extractor groove which instantly disassembled the magazine. Again, no damage to the gun or actually even the magazine once I found all the pieces and reassembled it.
I've fortunately never experienced the sort of failure like the OP where the gas seal was breached sufficiently to dump a lot of gas back into the action.

 

[CLT65]

It happened about 20 years ago, with a round of the now-infamous TZ80 Israeli ammo. The case split clear across the web, a huge crack right into the primer pocket. I still have a photo somewhere if I can find it. It was no fun at all.

 

[WAW44]

She's back... Already test fired 20 rounds.
I wish I could take the credit, but it was all done by the folks at Bullseye in Tacoma.

 

[Hummer]

Is this what your fired case looks like?

 

[WAW44]

yes

View attachment 642479

Is this what your fired case looks like?

 

[WAW44]

Nope. The only casualty was the birch stock. Replaced with a USGI walnut stock by an armorer, who also changed some other worn out bits that were not connected to the incident, and given a good bill of health after test firing 20 rounds. Underwear was bleached.

And underwear......

 

[WAW44]

 

[Hummer]

Typical soft head failure. Case went though annealing mouth down and head got heated and softened.

 

[CLT65]

Here's a rainy day project. When I get time, I'll pull them all down and load the powder and bullets into good brass. I'll decrease the powder a little; no need to beat up the old M1.

 

[Hummer]

Also take a hammer and flatten the mouth/shoulder. If you are going to use a collet puller run the rounds up in a bullet seater and reseat them about 1/16". You should hear a little crackling noise as the mouth lacquer is broken loose. Then pull the right away before the lacquer resets.

Or you could drill 1/8" holes in the cases about 1" forward of the rim and make dummy ammo out of them and save the propellant.

For the Garand I would reduce the charge about two grains and that will lower your port pressure. On the 30.06 Match ammo I pulled down it has 46 gr. 4895 in them and I reduce it to 43.3 and it groups much tighter with no pressure spikes.

Then take my pic and your pic and start posting them on other forums.

 

[Nibbs]

I has stocks n parts if you still need any.