M1 Garand + Schuster gas plug questions

[0to60]

Schuster's directions say the thing is shipped fully "open", meaning the autoloading mechanism will not work. One is to gradually tighten the adjusting screw until your rifle is functioning correctly.

When the plug is wide open, is the rifle effectively a single shot, bolt action rifle? The autoloading mechanism is bypassed completely? If semiauto firing weren't important to me, could I load up rounds however I want (as far as bullet weight and powder burn rate, even loads that aren't suited to M1s)? Could I neck-size-only my brass?

 

[horsemen61]

I wouldn't but that's just imho

 

[macgrumpy]

Yes, it would be a single shot rifle.
No, you shouldn't load ammo that's hotter than recommended - the bolt and receiver lugs will only hold up to their designed parameters.

 

[0to60]

I don't mean "hotter than recommended". The M1's gas system is such that it likes a fairly narrow range of burn rates. Varget, one of my favorite powders, is outside this range. Would I be able to safely shoot Varget loads (I always load near minimums, especially for older firearms) if I run the Schuster wide open, as a single shot rifle?

 

[scythefwd]

yes, you could load with whatever powder you desired. The narrow range is due to gas port pressure and damage to the oprod risked... If your oprod isn't in play, then no reason you cant use the full range of 06 capabilities as long as you keep it safe ..

 

[Llama Bob]

I agree with scythefwd. My understanding is that with an adjustable gas plug, you can even shoot Varget loads as an auto without bending the OP rod. Hopefully someone can confirm.

 

[ROAshooter]

that is the point of the schuster plug....to give you the capability to use a variety of bullets/powder.....just dial it in till the rifle functions as normal...

 

[25-5]

I have used Varget for years per The Hornady 9th Edition manual specific for the M1 Garand. Never had anything close to a problem. Same deal for the M1A. 168gr SMK or A-Max.
I used the Shuster at times on each rifle. Found no real need for them, so took them off.
The 4895's are great too.

 

[macgrumpy]

As said already, the limited selection of powder is due to the potential of bending the op rod, if the gasses are vented enough to prevent the op rod from functioning then there isn't any potential for damage.

 

[agtman]

I have used Varget for years per The Hornady 9th Edition manual specific for the M1 Garand. Never had anything close to a problem. Same deal for the M1A. 168gr SMK or A-Max. I used the Shuster at times on each rifle. Found no real need for them, so took them off.

For several years during the Nat'l Matches on Commercial Row, you could pick up a "mini" Service Rifle reloading booklet at Hornady's station in one of the buildings there. The booklet contained Hornady's data for handloading all the typical match loads, with bullet-weights and powders listed for the AR, M1A, and M1 Garand. Varget was one of the propellants listed.

 

[Slamfire]

Could I neck-size-only my brass?

Don't ever neck size for this rifle unless you want to have an out of battery slamfire which knocks the back of the receiver off!




Projectile: Milsurp 147grn FMJBT
Primer: Federal standard large rifle
Case: HXP 68 (it has been loaded at least 4 times all necksized only after being fire formed)
COL: 3.292 (sample of lot that left)
Powder: 48 grains of IMR 4895
Dies: Lee neck sized

This is an M1 carbine receiver, easy to understand, functionally no different from a Garand. Notice that between the red lines nothing prevents the firing pin from making contact with the primer. You can take your Garand action out of the stock and verify the same condition.



This mechanism does not have a positive firing pin block, that firing pin is rebounding off a primer throughout the complete feed cycle, which is one reason you see a firing pin dent on the primer of a chambered round.



If you happen to have a real sensitive primer, and your case has been full length resized so that the lugs go into battery without any delay, your chances are good that you will have an in battery slamfire. But, if you neck size such that the bolt has to crush fit the cartridge to the chamber, that firing pin is rebounding off the primer, at the highest speed in the feed cycle, and your lugs are not engaged. If you have the bad luck to have a real sensitive primer than your chances are good to have an out of battery slamfire. With the exception of roller bolt mechanisms, all semi auto rifle mechanisms have the chance to slamfire, because they don't have firing pin blocks, and if the firing pin rebounds off the primer, they all will slamfire. Most of the later semi auto mechanisms do have safety features to prevent firing pin contact between firing pin and primer when the bolt is out of battery. There are lots of AR15 slamfires but that mechanism positively keeps the firing pin behind the bolt face, so AR15 slamfires are in battery. (might be a couple of out of battery but it was not due the firing pin) The perversity of the Garand mechanism, that is M1 carbines, M14's, M1a's, mini 14's, is that this mechanism allows contact between the firing pin and primer all the way to cam down. Therefore, full length resize and use the least sensitive primers you can buy. I recommend the CCI #34 primer or the Tula mil spec. Less sensitive is better than more sensitive.

 

[Reloadron]

These are M1 Garand service rifle loads. They are based on the Hornady 9th Edition load manual. Load as you normally would using the suggested loads. This is the load data agtman mentions. Covers 30-06 Springfield and 308 Winchester. The link does not extend to .223 Remington loads yet.

If you ever have concerns about slamfires just use primers designed for military rifles using a free floating firing pin like CCI Available in large (No.34) and small (No. 41) rifle primer sizes.

Yes, with the plug wide open you have a single shot rifle, as if there was no plug at all. However, loaded cartridges should be full length resized and loaded as normally.

Hope the load data helps.

Ron

 

[30Cal]

If you get a sticky case with the gas system disabled, you're going to have to pogo-stick the rifle to get it open again. That oprod handle has only a tiny fraction of the mechanical advantage the the bolt hand on a bolt action rifle has.