Gas Leak: Gas Tube Pin Burnt Up/Corroded?

BenL · Jul 22, 2015

I shot a 3 gun match on Sunday (Heavy Metal) and after the match, a few of us hung around and shot distant steel for a few minutes.

During that after-match practice, my 308AR started having problems: would eject but not strip off the next round or lock back on an empty mag. Definitely a gas issue. When I got home, I pulled off my handguard and found this:

Definitely bleeding gas. If you look closely, it looks like the pin is either burnt up or corroded away.

Is it a safe bet that my gas block is probably fine and I just need to replace the pin? Background: When I first got it, the gun was originally over-gassed, so I put in a Heavybuffer (heavybuffer.com), which fixed the issue.

Also, when I measured the base where the gas block slides on, it measures .735, not .750; is that area usually tapered? If the consensus is that the gas block might be toast, I may replace with an adjustable gas block and swap out the heavybuffer.

clandestine · Jul 22, 2015

Tapered Gas Block Seats are not normal.

Is that Gas Block Aluminum? If so that's part of the problem. Aluminum heats and cools at different rates and will lead to leakage and erosion way more than steel or titanium.

If the gun was overgassed I would put an adjustable gas block to prevent this.

BenL · Jul 22, 2015

clandestine said:
Tapered Gas Block Seats are not normal.

Is that Gas Block Aluminum? If so that's part of the problem. Aluminum heats and cools at different rates and will lead to leakage and erosion way more than steel or titanium.

If the gun was overgassed I would put an adjustable gas block to prevent this.

OK, thanks Chad. It's a factory DPMS barrel that I had planned to replace over the winter, anyway. Guess it will come sooner. :thumbsup:

clandestine · Jul 22, 2015

If it shoots good a clamp on gas block from SLR will remedy the undersized journal, tapered journal, or overgassed issue. You can also reuse the gas block if you replace the barrel.

I'm not sure if a clamp on will clear your rail though.

BenL · Jul 22, 2015

For a factory barrel, it does shoot pretty well. I can check clearance when I get home; SLR has the dimensions of their blocks on their website (1.365" set screw vs. 1.40" clamp on)

Thanks again.

friendlyhippo · Aug 4, 2015

For the record, a heavier buffer doesn't actually FIX an overgas issue....it merely provides an expedient manner with which to deal with the symptoms. Rig is still overgassed, regardless of buffer weight.

+1 on a steel adjustable gas block.

BenL · Aug 13, 2015

Yes, I realize that. I guess I should have said, "the gun was overgassed and the bolt would occasionally fail to unlock. To remedy that symptom, I put in a heavier buffer to increase the dwell time."

On Chad's recommendation, I've since put an SLR adjustable gas block on it. I'll tune it this weekend. The real question is this: should I take out the heavy buffer I put in there and put in a standard weight buffer, now that I can adjust the gas flow?

I switched to a rifle length buffer tube, so right now, it has a Spike's spacer, extra power carbine spring and carbine heavybuffer buffer.

clandestine · Aug 13, 2015

That's your call. A heavier buffer will make it a little more reliable, but means more recoil impulse as the mass bottoms out under recoil. You will lose some adjustability with weak ammo with a heavier buffer.

A light buffer allows the most adjustability and less recoil impulse, but is slightly less reliable.

BenL · Aug 13, 2015

Thanks, Chad. :thumbsup:

Gas Leak: Gas Tube Pin Burnt Up/Corroded?

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