Shuster M1A adjustable gas plug

joshmb1982

Anyone have one of these on their rifle? I installed one on my SA M1A several years ago and forget which way to adjust it to shut it off and open. I can't find the instructions for it.

The last time I shot it I saw a couple of keyholes. I want to close it off and start over but can't remember if I need to "tighten " it to close it or if loosening it closes it.

Anyone know for sure?

Ditch-Runner

go to google lots of info here is just one




Image result for Schuster M1A adjustable gas plug INSTRUCTIONS



Start with setscrew at the factory preset position. Turning the screw about ? turn at a time, tighten screw, and fire until the rifle functions reliably with your particular load. If the adjusting screws seems to loosen , install the hollow locking setscrew and tighten against the original screw locking it in place.



M1A Adjustable Gas Plug - SCHUSTER MFG INC



www.schustermfg.com/m1a-adjustable-gas-plug/

joshmb1982

Didn't see that before. So sounds like I need to back the set screw all the way out to start over.

Thanks.

Ditch-Runner

glad it helped
I was thinking of getting one ( or like it ) for my m1a

joshmb1982

I'd say it takes a little more work then the description says.

First off it did not simply thread right onto my rifle. It was VERY tight. I was only able to start it about 1/4-1/2 turn and then had to oil it as I tightened and backed
Out. Tightened and backed out. Similar to tapping a new hole.

Then following their instructions i simply adjusted until the rifle functioned 100% and left it. The rifle was already sighted in when
I did this so I haven't shot paper since. Last year I shot on paper again and this is when I saw the key holes, so I'm going to tinker with it some more in its new stock and see how it does.

The set screw for the plug has clicks to it so it wouldn't be hard with experimentation to figure out where it is for your 180gr hunting loads and then just turn so
Many clicks back to 150gr ball ammo.

M1A762

You can shoot 168's without the adjustable gas plug. Not much game out there that can't be taken with a 168gr .308.

Maybe reconsider the Shuster plug and go with a USGI gas plug instead, no problems with the USGI system.

chiefr

I have seen the adjustable plugs cause FTFs and other problems but never a keyhole. Guess I learned something. Thanks

Horse Plains Drifter

I bought one too several years ago, but never put it in. After reading the SA M1A users manual, one can see it is not needed.

From page 5 of the users manual:

3. The M1A is designed and built to specifications to shoot standard factory .308 made to SAAMI specifications or 7.62x51 NATO ammunition. The specifications for standard military ammunition include harder primers to withstand the slight indentation from the firing pin when the bolt chambers a cartridge. This slight indentation is normal.
The use of civilian ammunition with more sensitive primers or handloads with commercial primers and/or improperly seated primers increase the risk of primer
detonation when the bolt slams forward. This unexpected "slam fire" can occur even if the trigger is not being pulled and if the safety is on. Use of military
specification ammunition will help avoid this. Every shooter should use extreme caution when loading this or any other firearm. See page 17 for instructions on
proper loading to help avoid a "slam fire". Also see enclosed article on "Slam Fire" written by Wayne Faatz

joshmb1982

quote:Originally posted by chiefr
I have seen the adjustable plugs cause FTFs and other problems but never a keyhole. Guess I learned something. Thanks


I assumed (could be wrong) that if it is either adjusted so it just barely functions or functions with to much force, that this could effect the harmonics and cause the keyhole?