Safe Ammo

[Interlake]

I have a 1943 vintage SA M1 I just got from the CMP. It came with an uncut op rod and I added a Shuster plug. What are the specs on ammo I can safely use? Is it just bullet grain and bullet speed or a combination of the two.
EX) Just got a box of Winchester Super X. 150gr 2920 speed and 2839 energy. Bullet weight is fine but othe specs seem high. What kind of parameters can I use> Thanks for your help in advance.
Ed

Information

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[Singer B]

I only use the American Eagle 150gr round that specifically states it is for the M1 Garand on the box. They are kind if hard to find, but better safe than sorry.

[browningautorifle]

If you have an adjustable gas cylinder lock screw...called a Schuster adjustable gas plug, you can use any ammo you like because you can allow excess gasses to escape. You simply vent them and adjust the Shuster to your current ammo. A real pain in the butt though, because you have to do that every time you change any spec on your ammo.

You can use ANY ammo you wish.

[Interlake]

Is that also the case with the uncut op rod and thanks for the responses

[browningautorifle]

uncut op rod

The uncut op rod could crack any time with any ammo. Or, it could function on for decades. I'd use a shooter op rod on a shooter rifle. I had a LL M1 SA 328219 and it had round firing pin, uncut op rod...and I didn't shoot it. I shot the other rifle. The one with common or replaceable parts. Others here will disagree.

[Ex Crab]

I go with browningautorifle. I have a Shuster plug fitted to my Garand. I use Prvi Partizan which is a bit hot and used to eject the cases a good 15 feet or more. The Shuster changed that to about 3 ft. When using my hand loads with 168 grn HPBT I don't need to change the setting unless it is very cold.
In short, the Shuster plug is the best thing since sliced bread.

[Interlake]

How do you define Garand Friendly ammo if not written on the box?
Will just a 150 gr bullet do or are the other considerations.

[Bob Womack]

One of the biggest issue is the speed of the powder burn. Modern ammo burns quicker than the original load, more quickly in fact than the Garand action can respond. What that speed is, I don't know. The technique with the adjustable plugs is to open the set screw way up* until the action won't cycle and then slowly close it again, 1/4 turn at a time, until it just cycles.

Bob


* The Schuster comes opened up already.

[browningautorifle]

open the set screw way up

Exactly, so it doesn't matter what you're using after that. The pressures will be low enough.

[Sunray]

"...specs on ammo..." The Rifle was designed and tested to use .30 M1 ammo not .30 M2. .30 M1 was loaded to duplicate the M1906 service ammo. It used a 174.5 grain bullet at 2800 FPS and was loaded to give more range in MG's. However, it was found it had too much range for the U.S. National Guard ranges so the Ordnance Board ordered a lighter bullet load. That was a 152 grain bullet at 2640 FPS. In 1940 the velocity was increased to 2800 FPS to match the ballistics of .30 AP and its 168 grain bullet.
Undocumented internet rumour has it that the M1 Rifle op rod can be damaged by using heavier than 180 grain ammo. Never seen nor heard of any such damage that was not totally hearsay on an internet forum in over 40 years. (I have personally fired 220's out of my rifle with no fuss. Wasn't a steady diet of 'em. They did truly astounding things to a ground hog.). Watch for the glib reactions here.
There is absolutely no documented ballistics lab testing that's ever been done proving anything one way or the other. And the whole thing has been argued about ever since.
However, the ammo used during W.W. II was called .30 M2. It used a 152 grain bullet at 2800 FPS with IMR4895 powder at 50,000 PSI.
JC took one of 'em to 120,000 PSI when the left locking lug cracked. He then fired a further 5,000 rounds of standard Service ammo, that'd be .30 M1, with no more damage of any kind.
Have a look here.
Ammunition for the M1 Garand