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Author Topic: Insufficient headspace M1 Garand  (Read 1159 times)

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Offline bearfat

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Insufficient headspace M1 Garand
« on: September 17, 2006, 06:02:23 AM »
I had a new barrel put on a M1 Garand. Too make a long story short several hundred rounds later I decided to reload some of the brass fired from it. I put a RCBS micrometer to the brass to check the headspace to find it averaged nine thousands below ANSI minimum. Plus I had bent rims (pic's below).

I'm not taking the gun back to the gunsmith because quite frankly I don't even remember who or where the guy was other than he came recommended for M1 Garand work by someone. He worked out of his house and it was a good 80 miles from here. I paid him cash.

Somewhere along the line I took the gas plug out making it a single fire and saved that brass in a different container. The single fired brass DOES NOT HAVE BENT RIMS but is below ANSI minimum headspace.

I never noticed any problems chambering rounds, military or commercial. I never had any jams from the brass failing to eject. Like I say nothing until unfortunately I ruined several hundred never fired brass and finally checked the headspace.

I do have two theorys:

1) The new barrel may have changed the timing in the gas pressure curve? The tight headspace has nothing or only some effect on the noted problem.

2) The tight headspace is the sole problem. The brass simply has not released itself from the chamber wall yet when it is being ejected.

Here is my question. I have plenty of new unfired Remington brass I have to full length resize anyway. Can't I just resize a couple hundred rounds ten thousands below ANSi minimum and use that brass only in the M1.

Am I off base? Comments?

 
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Offline Bad Flynch

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Re: Insufficient headspace M1 Garand
« Reply #1 on: September 17, 2006, 06:13:56 AM »
You don't state what you load is, and it could be as simple as powder of the wrong burning rate. Timing problems usually are a matter for a Garand specialist, however, and I am not one.
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Offline bearfat

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Re: Insufficient headspace M1 Garand
« Reply #2 on: September 17, 2006, 06:27:31 AM »
The pics are lake city DCM/CMP ammo 1972 and 1974 stuff.

The commercial stuff I fired thru it (approx 250 rnds ) was Remington UMC 150 gr FMC. The cheap stuff.

I have not really even thought about what a I was going to reload, whatever my NRA M1 Garand book said for a 150 gr bullet.

I want to use the M1 this fall for a rainy day deer gun.
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Offline Paladin

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Re: Insufficient headspace M1 Garand
« Reply #3 on: September 23, 2006, 02:57:56 PM »
the rims are bent the wrong way for the extractor to cause them, looks more like they hit a concrete floor when they were ejected
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Offline cwlongshot

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Re: Insufficient headspace M1 Garand
« Reply #4 on: September 23, 2006, 11:44:26 PM »
Because the gun is being used single shot with the gas piston removed. The problem is NOT the powder burning rate. BUT, it IS something to consider and be aware of if you dont want a bent op-rod when the piston is back in the gun!!

 I would have the guns chamber checked. I'll bet that is a put together gun and some of the parts are not just so.

The extracter may be long as well as a headspace issue with the barrel.  If the extractor IS long or not square, it could cause the bent rims as it would stand prowd of the bolt face upon full reward position. I would take a good look at that guns chamber. BTW, how are you deciding you have a head space problem? Are you ripping off case heads, or just ringing them?

CW
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Offline PaulS

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Re: Insufficient headspace M1 Garand
« Reply #5 on: September 24, 2006, 08:08:01 PM »
If there is no operating rod then you should be able to open the bolt slowly - catch one in your hand and see if it is there. If it isn't there when you operate the action slowly then it might be due to the ejector when the bolt is operated fast. If it is there then it has to be something on the bolt that is causing it. Try slipping the round into the extractor and let the bolt hold the case as it goes in to the chamber. Fire it - If it isn't there then the extractor is a probable cause. You could also feed a round through the action without firing it (loaded the way that you normally load when you find the bent rims) ejecting the live round to see if it is bent. If it is then you know it has to do with the face of the bolt - probably the extractor bending it as the bolt comes forward.
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PaulS

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Offline Grumulkin

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Re: Insufficient headspace M1 Garand
« Reply #6 on: September 25, 2006, 01:25:59 AM »
The rims are not bent from the ejector but from the bolt slamming into the cartridge to chamber it (the normal thing to happen in an M1 or M1A).  I don't think it's a headspace or really any problem at all.  If a chamber has too little headspace, the rounds will not chamber easily.  If it has too much, the result is blown primers and/or case head stretching or separation.

How many of you guys have actually shot an M1 or M1A?  Look at the case heads and they will look similar to what's in the photos.
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