Problems with Schuster DCM Gas Plug

[Daimler1989]

Hello,

some time ago I was advised in this forum to mount an adjustable gas plug on my M1 Garand chambered in 308 to make it function. With some brands, the rifle does short stroke, with some other, obviously stronger ammo, it functions well, but accuracy is not the best. So i installed the Schuster DCM Gas Plug and tried to adjust it. Not way to get the gun cycling flawlessly. I turned the setscrew in, until there was no more movement possible, and now the screw is half way out of the backsite of the plug, and the gun is still short stroking. Or did I turn the wrong way? I guess it was right, to tighten the screw, i.e. not to turn it out in direction of the muzzle. Or is it my rifle that is beyond function with certain brands of ammo ?

Any help appreciated
Ulrich

Information

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[Phil McGrath]

Its my understanding that your suspose too screw the adj screw OUT this adds volume too the gas cylinder, if you have screwed the adj screw in you have made the volume of the gas cylinder smaller.

I would start with the adj screw removed from the plug, then install it and give it a 1/2 turn to the inside untell the rifle starts too function when it wants too start working with regularity try a extra 1/4 turn as a just in case after that you should be done. If you switch ammo all bets are off you will need too start over again.

The trick with these plugs is too give the rifle just enough gas too make it work with heavy bullets without beating the action or bending a op-rod, if your just shooting std M1 Ball or reloaded ammo with powder in the right burning range at nominal muzzle velocities, why look for a fix in need of a problem?

[Daimler1989]

Hi,

thanks for your input. Problem with my M1 is, that it doesn't fully cycle with standard 7.62 NATO ammo (next round doesn't chamber) and handloads with heavier bullets (170 grs) even with near max loads. There are only two or three brands that work properly and that's not what I expect from a rifle I want to rely on.

Now my problem is: I DID turn the screw in, not out, and it is screwed all the way in and backs out from the plug. There is no more way to screw it in farther. But the rifle is still short stroking.

regards
Ulrich

[us019255]

Is the op rod moving freely? Do the "tilt test" which is explained in many threads.

[Phil McGrath]

#1 maybe you have screwed it in too far and have covered part of the gas port in the barrel or #2 the gas cylinder is not lined up with the gas port in the barrel, #3 mic the button on the end of the op-rod .526 too .525 is about the norm if its smaller than .525 you could have have gas blow by and need a new piston or op-rod replacement if its cheaper, also the port in the barrel should be .090 and last check maybe the gas cylinder is just worn out and needs replaced?

What brand of ammo and what is your reload data 170's are not that heavy and should work well in your rifle.

What brand barrel does your rifle have?

[browningautorifle]

I use a standard gas cylinder lock screw relief valve in my 7.62. I shoot LC match and IVI ball with no problems. I have a Kreiger barrel that was brand new when I installed it. 3,340,000 rifle. I think you're reading something into this that's not there. Here in Canada those plugs aren't commonly available and we don't have bent op rods to show for it. I wish this hype would just blow away.

[Daimler1989]

Thank you all,

I checked the gas cylinder today and found quite an amount of black residue where the gas cylinder sits on the barrel. Around the fastening grooves and the lower side of the barrel were black with powder residues. So I guess, there is substantial gas blow by at this place, and this is why the Schuster Gas Plug could not work. Does this mean, the gas cylinder is out of spec and affects the function of the rifle? Probably the problem will aggravate with continued use...

Any ideas?

regards
Ulrich

[browningautorifle]

Original parts work fine with GI ammo form CMP. That is providing they're within spec. If you need a new gas cylinder, they're available.

[jmoore]

Daimler1989 's in Germany, so the CMP won't be much help...

A couple of thoughts:

What size is the gas port in the barrel? Generally, the 7,62x51 Garand needs a bigger port.

The adjustable gas plug won't add operating power to the gas system! So it's addition cannot but make any loads less likely to cycle. It is intended as a power reducer.

[browningautorifle]

I don't know why I didn't catch that. Normally that's the first thing I check. Therefore most of my info to him is BUNK! He MAY need a new gas cylinder though. Provided he uses standard M2 power loads, and they don't cycle that would be the case. If he replaces the gas plug with the original it may just work fine.