Garand History

If you don’t what to believe that IMR 1185 is a slower propellant than IMR 4676 or IMR 4895, that is immaterial to my point.

My point:

There are some people that state because the M1 was designed to work with M1 Ball and its heavy bullet, the use of heavy bullets and slow propellant will not pose any problems.

This statement is based on a false assumption, in that the M1 gas port system was not designed with M1 Ball, but the lighter bulleted M2 Ball. We know this because all of the reports from 1939 onwards on the reliability and functionality of “new” M1 rifle gas system specifically states the use of M2 or proto-type M2 ammunition. The first major report was done at Ft Benning and published in Dec 1939 goes to suggest some minor changes, indicating the system was close to being under gassed. Which leads to the Aberdeen report in which the attempts to establish minimum port pressure for reliable operation. This is followed by a change to the drawing dated March 1940 that increases the gas port diameter from 0.069” to 0.079”.

The M1 gas system we know today and was used throughout most of the M1’s life was not designed around M1 Ball, but specifically tailored to M2 Ball, and specifically M2 Ball using medium-quick propellants like IMR 4895.

So, for best longevity of the operating rod and associated parts, the barrel pressure at the gas port location should be kept between 7,500 psi (the minimum from the Aberdeen report corrected from muzzle pressure) to 9,500 psi (also from the Aberdeen report, the maximum pressure observed from M2 Ball ammunition, again corrected from muzzle pressure).

EDIT: And, the maximum observed pressure was from IMR 1185, if you think that value is too high, then the maximum port pressure should be bumped down accordingly.

lysanderxiii said:

Those are headstamps, not lot numbers. In short, you have no idea what propellants are actually in them.


Let's see, on one hand:

I have a report from a reputable testing facility that had been testing weapons for years (Aberdeen Proving Grounds, Aberdeen, Md), that gives me all the background information, such as set-up configuration with multiple weapons, ammunition from know lot numbers and propellant types and with known storage condition histories, shooting a few hundred rounds to get a average, and exact details (such as make a model of pressure gauge, amplifiers and filters) stating that M2 Ball (150 gr) loaded with IMR 1185 has a muzzle pressure averaging around 11,200 psi.

On the other hand I have somebody of unknown qualification, shooting a half dozen rounds of ammunition, from unknown lots, loaded with unknown propellants, that is nearly 100 years old, stored in unknown and unrecorded conditions for most of that time, fired from an unknown test set-up, with unknown equipment telling me the original report is wrong. Not to mention the ammunition used here is M1 ball with a 174 grain bullet.

Okay, whatever.

Click to expand...

Uh...no...I said I had lot#s in my notes...those are the YEARS I tested. And yes its IMR 1185.

If you have these notes of the test setup...share them with us.

My testing was done in a qualified ballistics lab that can do all types of testing in regards to internal ballistics. Test barrel was specially made to the min spec on the prints.

So again...1185 doesn't generate the port pressure you claim.

lysanderxiii said:

If you don’t what to believe that IMR 1185 is a slower propellant than IMR 4676 or IMR 4895, that is immaterial to my point.

My point:

There are some people that state because the M1 was designed to work with M1 Ball and its heavy bullet, the use of heavy bullets and slow propellant will not pose any problems.

This statement is based on a false assumption, in that the M1 gas port system was not designed with M1 Ball, but the lighter bulleted M2 Ball. We know this because all of the reports from 1939 onwards on the reliability and functionality of “new” M1 rifle gas system specifically states the use of M2 or proto-type M2 ammunition. The first major report was done at Ft Benning and published in Dec 1939 goes to suggest some minor changes, indicating the system was close to being under gassed. Which leads to the Aberdeen report in which the attempts to establish minimum port pressure for reliable operation. This is followed by a change to the drawing dated March 1940 that increases the gas port diameter from 0.069” to 0.079”.

Click to expand...

Yeah they had to open the port up because M1906 spec ammo didn't have the gas volume to reliably operate the rifle in adverse conditions. This is another reason why M2 ball velocity was upped from 2700 at the muzzle to 2805. To better match ballistics of the AP ammo AND it also provided more gas for the system to operate.

lysanderxiii said:

The M1 gas system we know today and was used throughout most of the M1’s life was not designed around M1 Ball, but specifically tailored to M2 Ball, and specifically M2 Ball using medium-quick propellants like IMR 4895.

Click to expand...

You mean IMR 1185 since thats the powder used in the new M1906/M2 ball.

lysanderxiii said:

So, for best longevity of the operating rod and associated parts, the barrel pressure at the gas port location should be kept between 7,500 psi (the minimum from the Aberdeen report corrected from muzzle pressure) to 9,500 psi (also from the Aberdeen report, the maximum pressure observed from M2 Ball ammunition, again corrected from muzzle pressure).

EDIT: And, the maximum observed pressure was from IMR 1185, if you think that value is too high, then the maximum port pressure should be bumped down accordingly.

Click to expand...

Odd...they would set that limit and then allow factories like DEN, UT, SL, DM and probably LC and WCC/WRA as well to exceed that 9500 psi limit. FYI DM 42 M2 ball is 10,600 psi at the port while SL AP is 9965.

I wonder if you think PPU and S&B got it wrong as well when they made their "garand" ammo? Since BOTH of them exceed 10,100psi at the port.

Needless to say actual test results from modern test equipment in a modern ballistics lab are rapidly shining light on decades old myths.

Jeremy2171 said:

odd...they would set that limit and then allow factories like DEN, UT, SL, DM and probably LC and WCC/WRA as well to exceed that 9500 psi limit. FYI DM 42 M2 ball is 10,600 psi at the port while SL AP is 9965.

Click to expand...

Again, reading is fundamental.

I never said "they" set the limit, I stated my recommendations for modern ammunition used in a rifle that is 70 to 80 years old. And, the fact that operating rods are not as plentiful as they once were.

Jeremy2171 said:

Yeah they had to open the port up because M1906 spec ammo didn't have the gas volume to reliably operate the rifle in adverse conditions. This is another reason why M2 ball velocity was upped from 2700 at the muzzle to 2805. To better match ballistics of the AP ammo AND it also provided more gas for the system to operate.

Click to expand...

Which further indicates that the system was designed for M2 ball.

4v50 Gary said:

Doesn't Collectors' Grade Publication have a book specifically on the Gas Trap Garand?

Click to expand...

Yes, they do.

Gas Trap M1 Garand – Forgotten Weapons

rust collector said:

If anyone has more information on the different types of gas cylinders, let's hear it.

Click to expand...

rust collector said:

The OP was about the different types of gas cylinders in early guns. If anyone has more information on the different types of gas cylinders, let's hear it. Otherwise, this thread seems to have outlived its usefulness.

Click to expand...

I can get more pics of mine if that will help...