308 Garand Short Stroking

[jbkf1003]

I have a 308 Garand I built from a barreled receiver using a criterion 308 barrel. (Tim installed the barrel and reparked the receiver). I shot it the other night for the first time, It shot well, and was very accurate. But it was short stroking (atleast I assume, I had empty chambers 2-3 times per clip) with PPU M80 and my Handloads 42.1gr H4895 under a 150gr FMJ. Federal XM80 worked flawlessly but I only had 20 of those. Criterion states the gas port size is .086". The gas plug was a little loose I noticed after I got it home. Not like falling out, and it was all the way in but I could turn it with my fingers. I remember just finger tightening it when I built it because I had to get a 1/4" socket extension to tighten it down. I forgot about it before I shot it.

I hear .086" is a bit small. My question is should I open up the gas port or assume the issue was due to the loose gas plug? is .086" too small anyways? If I were to open it up can I do this at home with a hand drill in a gun vice or do I really need a drill press. (I don't have one).

Thanks Guys,
Justin

[timshufflin]

I would go to 3/32" and call it a day. Just do it with a hand drill, you really can't screw it up. Heck, I can do it.

[jbkf1003]

Will do.
Thanks for the offer, but I'm not shy, I'll drill away.

Thanks,
Justin

[timshufflin]

Will do.
Thanks for the offer, but I'm not shy, I'll drill away.

Thanks,
Justin

I met that even I can do it. Nothing to it.

[timshufflin]

By the way, if you still have a problem, you could just keep going up to .099 with no problem. I wouldn't be concerned about going as large as some of the GI 7.62 Nato barrels which climbed to as high as .118 if the rifle is full length. Overall though, the smaller the hole the better.

[Phil McGrath]

By the way, if you still have a problem, you could just keep going up to .099 with no problem. I wouldn't be concerned about going as large as some of the GI 7.62 Nato barrels which climbed to as high as .118 if the rifle is full length. Overall though, the smaller the hole the better.

I think the USGI spec for mid production 7.62 SA barrels was .1065. The late Rock Island barrels made for the AirForce team were .099

[timshufflin]

I like .099 as well too but if I can get away with 3/32 then I do.

[jbkf1003]

Hi Guys,

I got out to shoot the 308 Garand the second time since I opened up the port to 3/32". XM80 and PPU M80 shot fine. The PPU is now working. My handloads did not. Originally they were 150gr Hornady FMJ over 42gr of H4895 in LC brass. I loaded up the same load with 43gr of H4895 and still have problems. Out of 4 clips, 1 clip fed all 8, 2 had 1 short stroke, and 1 had 2 short stroke. I will primarily shoot surplus, but supplement with my handloads when price / availability are a problem. What do you think? Open it up more? Or load up my handloads to higher pressure? I know 43gr is still a bit on the low side.

A schuster is also an option? Can you set it to bleed off LESS gas than the GI plug thats in there now?

Thanks
Justin

[timshufflin]

The Schuster would only work if you already had too much gas. The schuster will not give more gas than any other screw.

Your options are;
1. You could open the port up to as large as .118
2. You could check your oprod piston and see what it mics. You could try to find a piston at the higher end of .526.
3. You could mic your gas cylinder and see how tight that is.
4. You could make sure that there are no cracks in the bottom of your gas lock screw.
5. You should make sure that you have absolutely no rubbing on your oprod by your stock or stock ferule.
6. You could shoot a used GI oprod spring that measures well. The GI spring will probably cycle easier than any new spring.

[jbkf1003]

Ok I will take a look for rubbing, and measure the piston. The Gas Cylinder and plug were NOS so I'm assuming they are ok, but I'll take a look. Stock fitting could be an issue, it was a new CMP stock set.