The difference between a loose gas cylinder and a peened one on accuracy.

[WarPig1976]

Took the M1 out yesterday for the first time since I peened the cylinder splines and used cork gasket material to snug up the action.
I haven't had this rifle a year yet and took it out maybe 3 times. Every thing seemed tight to me so when I really wasn't that happy with its accuracy I blamed the ammo which are my handloads. Turns out the gas cylinder WAS loose, it only moved a gnats whisker which was enough to really effect accuracy as I found out.

This is a target I shot when I first got it.
Attachment 46802
This target I shot yesterday. The 7 below the 10 ring are "rapid fire" if I took my time all would be in a 3" group. Needless to say I'm very happy.
Attachment 46803

Information

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[Bob Seijas]

FWIW verticle stringing is sometimes poor breath control. You can see it if you aim at the target and breathe in and out... the sight blade will move up and down across the bull. Horizontal strings often result from flinching or jerking the trigger. At least that's what my Sergeant told me in 1960

[browningautorifle]

At least that's what my Sergeant told me in 1960

And he was correct...

[Comrade Mike]

What's the proper tightness for the gas cylinder? Mine has shot its way loose before, anyway to prevent this?

[WarPig1976]

It can't move at all. To tighten it you have to peen the splines, I used a ball peen hammer the round end of course and tapped it with another hammer. One doesn't have to hit hard either "learned that the hard way". I had to tap the cylinder on with a dead blow hammer. I suppose this has to be done every once in awhile because it was obvious it was done to my rifle in the past.

[no4mk1t]

Warpig, peening the splines is just one thing you can do to improve how a M1 shoots. You might find some other helpful tips in this thread.
How to Make an M1 Shoot Better

And if you are looking to improve the trigger....
How To Improve an M1 Trigger

[WarPig1976]

I just can not believe the difference in accuracy the tiniest of movement can have on the rifle. But as they say "the proof is in the pudding" or something like that.

[WarPig1976]

Is there supposed to be a O-ring between the gas plug and cylinder? I don't have one and the plug keeps loosening up.

[Bob Seijas]

No, and it's a gas cylinder lock screw, not a plug. FWIW that term is reserved for the Gas Trap false muzzle. Go to theGCA.org and click on Glossary of terms.

[emmagee1917]

Just smear a bit of the garand grease in the last two / three threads of the screw ( threads furtherest forward when shooting ) . That should keep her in place . If you do more threads , you'll cuss like a Marine getting her apart.
Chris