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Discussion Starter #1
I have a Springfield NM M1A that I've had since the early '90's and haven't fired it. That's about to change but I have been thinking I'd like to switch out the gas plug for a Schuster adjustable one and was wondering if it's a straight swap-out part? I have kinda gathered that some OEM gas plugs might be "fixed" in place and was also wondering how you can tell if that might be the case.

Thanks guys!
 

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An adjustable gas plug is necessary for a Garand, because the cylinder does not have a bleed.

The M14 gas cylinder has a hole to allow excess pressure to escape after the travel of the piston.
 

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Discussion Starter #3
Thanks for the reply... are you saying that an adjustable gas plug isn't necessary for the M1A? I plan on shooting 168/175 grain bullets.
 

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It isn't necessary, but it makes things a little easier on the op-rod. It is a drop in fit for US rifles with standard threads. It may not fit some Chinese gas cylinders with metric threads.
 

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...I have been thinking I'd like to switch out the gas plug for a Schuster adjustable one and was wondering if it's a straight swap-out part? I have kinda gathered that some OEM gas plugs might be "fixed" in place and was also wondering how you can tell if that might be the case...
If by "fixed in place" you mean almost impossible to get off, you'll know as soon as you try.GI2

The standard gas plug is suitable for standard ammo; an adjustable gas plug allows you to shoot heavier rounds with less risk of damage, but the trade-off is some chance of failure to cycle on standard ammo. The Schuster works through a combination of venting and changing the size of the gas cylinder/gas plug chamber that the gas builds up in before there's sufficient pressure to begin the cycling process. You can adjust for different loads but there's a locking ring that holds the adjustable part of the plug in place and removing that often changes the setting in the plug so adjustments for different loads aren't always repeatable (i.e., you have to re-establish the correct setting when you change ammo; it's not like just turning a dialGI4).

BTW, welcome to TFL!!
 

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I broke my M1A's original op rod shooting 180 grain Sierra matchkings with IMR 4350 powder. Cracked it, had it welded and it cracked again.

Then I read an article in one of the gun magazines (about 1982 or 1983) that said slow burning powders were bad for M1's and M1A's as they raised the gas port pressures above acceptable limits. Chamber pressure was well below max but the slower burning powders meant the pressure peaked later and did not drop off as fast as the faster burning powders like IMR4895.

I will not shoot such loads in my rifle again with out a Schuster gas plug.

As I truly believe every rifle is different you may get away with it.
 

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Discussion Starter #7
Thanks for the additional replies! A lot of information in the forum from a lot of you guys that have been there, done that. I will go ahead and replace my standard plug with the Schuster one as I will be shooting loads heavier than standard ball.
 
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