OK...so I finally have my M1.

[Slamfire]

Damage is not only limited to the Op Rod but "can' crack the receiver heel from the bolt slamming into it at high speeds from excess pressure to the gas system
Metal fatigue doesnt happen overnight and is accumalative.

This guy had his receiver crack with HXP 69. Greek ball.





I load my Garand ammo with a 168 match, 47.0 grains IMR 4895/AA2495, LC cases, CCI #34's.

With a 150 grain bullet I will bump it up to 47.5 grains.

Cutting these loads by a grain won't hurt a thing.

The original M1 and M2 ball loadings never exceeded 50,000 psia, often the pressures were in the mid 40's. Modern 30-06 is magnum level by comparision to the 1936 loads.

 

[Quoheleth]

The original M1 and M2 ball loadings never exceeded 50,000 psia, often the pressures were in the mid 40's. Modern 30-06 is magnum level by comparision to the 1936 loads.

You know, it's interesting you say that because the opposite seems to be true in the handgun world. Just a few minutes in the revolver forum will find someone who is lamenting how modern .357 Mag velocities aren't close to what they were back in the good ol' days.

Anyone want to speculate: how/why rifle loads are cranked up hotter (see quote above), but pistols shoot with less pressure/velocity? (This is a serious question, and neither intended to point criticism at Slamfire nor to anyone else).

Q

 

[jpwilly]

First, Let's clear something up there are two types of pressure units
"CUP" and "PSI".

The two are not the same!

CUP reads as PSI and the transducer method reads as PSI, BOTH readings are PSI and the Army NEVER changed the way the manuals are written which are “copper units pressure” (CUP) reading in pounds per square inch.

CUP is derived from a copper crusher, and is much less sensitive than the newer transducer derived PSI. The location from which the measurements are taken are different.

The newer transducer derived PSI measurements allow the recording of the pressure rise and fall in graphical format, to show peak pressure and pressure curve duration, as well as residual exit pressure levels.

M-1 Garand shooters are familar with residual exit pressure leves often refered to as "Port" pressure. It's the culprit behind bend Op-rods if it is too high.

For the .30/06, 62,500psi is generally considered max. 50,000cup is SAAMI max. for the '06.

The military really screws things up listing loads that were tested using the copper crush method but listing them with "PSI" when really they should be shown as CUP if SAAMI had anything to do with it (Hint they didn't exist back then)! Now that you understand why.

The M1 Rifles action and barrel are very strong. Stout as a bolt action IDK but IMO the rifle needs to be set up for whatever your shooting and it appears even some M2 ball can break an M1 rifle. Eventually rifles that are shot wear out. My money is on M1's running adjustable gas plugs lasting much longer if set up right.

 

[junkman_01]

There's no 30-06 shooting 150gr bullets at 2700fps with only 50,000PSI you really should read that as 50,000CUP.

Here's a load I've been shooting in my Garand for years. Quickload software says it's SAAMI using a transducer and it is a 150 grain FMJ bullet using 48.0 grains of IMR4895 going 2702 FPS and it develops only 39466 PSI chamber pressure. It has never damaged a Garand that I know of.......

 

[Col. Plink]

It's true: +1 on the surplus made for the M1 Garand.

I have lots of the HXP from Greece (1980 manufacture) and was hiting man-sized targets with original sights at 200 yds yesterday with relative ease (though it was windy).

 

[dmazur]

First off, rifles have CHAMBERS not cylinders. Secondly, what the heck are you talking about? The chamber pressure of M2 Ball ammo is around 40000 psi. What's with this "+/-2000psig" stuff? A 'tolerance' has to be stated to be of some value. It is not a stand alone as you have stated.

I think the concern is about the Garand cylinder pressure, which isn't a simple function of chamber presssure but is also related to bullet weight and powder burn rate. And the Garand has a gas cylinder as well as a chamber.

I found this reference in a Garand troubleshooting link. I can't confirm the 6000 psi figure, but it isn't totally unreasonable.

Garand troubleshooting

Part way down, under "short recoil", it describes "Gas port pressure should be 6000±2000 p.s.i."