Something that you may want to know on a short cycling rifle

[timshufflin]

Have any of you ever had a rifle that short cycled with marginal ammo and ran great with some HXP? A little diddy that Stu discovered was to simply back out the gas lock screw one turn thus creating a larger front chamber in the gas cyclinder. I noticed this thread on the CMP today http://forums.thecmp.org/showthread.php?t=43109&page=3

Stu told me about this little trick about three months ago while he was at the range. I've tried it on many shortcycling rifles that customers have sent me and it has worked to make them cycle in all but one case. That rifle had an oprod spring which was 2" to long????

This makes me believe that Erics gas lock screw with the larger front end will do what he says it will do. It would probably also make a rifle that otherwise shortcycles, now cycle.

[howie]

Wouldn't the looser screw have a tendency to back itself all the way out?

[canes7]

I am not familiar with Eric's gas lock screw, but I had read an article about how gas cylinder volume effects accuracy. It seems that one fairly popular Garand builder (name escapes me) had a rifle that just wouldn't shoot as well as he thought it should. After many failures at trying to fix the problem he thought that perhaps if he could delay the op-rod motion.

He took a solid screw, took some metal off the inside face and viola, the accuracy of the rifle increased. I haven't tried it yet. I doubt I have a way of accurately measuring any improvement.

I just checked the thread. In essence this is what the Garand builder in my story above did, just not to such an extent.

[timshufflin]

Yah, what I'm saying is that you can just increase the volume by simply backing out the gas lock a turn, so long as the port still shows. Howie, I've just not ever had an issue with gas lock screws backing out.

Want to make sure a gas lock screw does not back out? Hit the threads with some paint and let dry, now screw it in.

[Orlando]

Howie
I think he means back off the lock along with the screw.
Right Tim?
My question is why is the rifle short stroking to begin with, is this just a bandaid for undersized or worn gas cylinder that is acausing short cycling?

[howie]

Thanks Orlando. That would make sense.

[Punch The Clown]

I did this on a rifle with a marginal gas cylinder. Just loosened the lock 1 turn and re-tightened the screw. I think the big help was that the piston now was in a better part of the gas cylinder but who knows?. Anyway, the gun runs fine this way and short-strokes with the lock turned 1 turn in.

[timshufflin]

Howie
I think he means back off the lock along with the screw.
Right Tim?
My question is why is the rifle short stroking to begin with, is this just a bandaid for undersized or worn gas cylinder that is acausing short cycling?

Bandaid? I don't know. The rifles I've seen had pistons and gas cylinders in spec along with brand new oprod springs, no rubbing, perfect tilt. Were the specs on the piston and the cylinder on the low side? Yes but they were in spec. This issue seems to rear its ugly head with certain ammos.

Yes, I'm talking about the gas lock. Please forgive my poor use of nomenclature.

[Orlando]

I'll have to remember that trick
Thanks

[Punch The Clown]

Now, will an M14 gas screw fit an M1? I don't have an M14 so I can't try.