Problem with new AR- gas block?

[NyleRN]

I promise that's not always true.

In fact, about 2 weeks ago I had it actually happen to me for the first time ever... the clamp-on block on my 308 moved from where I had it set back against the shoulder, and it quit working. I put 0.30 gap back in and it worked again (ive since been reading that company supplies junk screws that stretch w/ their block)

~2x the diameter is only true in certain cases, eg carbines w/ .060-.065-ish ports, you might get away w/ it there depending on how well everything is cut. I recall somewhere around .090+ on a rifle port to into ~.120 on most blocks, i.e. def not 2x. going from memory so can't recall exactly. but that says you'd get 0.015+ overlap when pushed back...

plus pre-dimpled barrels usually assume the ports directly lined up to center the set screw, so you get best contact w/ the gap, regardless of alignment.

for the OP, all this is into the minutia. push it back or leave a gap, whatever... try it and see, or call the manufacturer and see what they say.

-rvb

I said almost twice the size. I can only speak from my experience. I've put about 15 ARs together and troubleshot a few others for friends with gas related issues. I have yet to see any overlapping with the block against the shoulder. But my sample size is only ~18. So sure it's possible I suppose. With folks making barrels with oversized ports you could ever so slightly overlap and still have enough gas to cycle the gun reliably. Of all the ones I've troubleshot they were Mid-length and mic'd .075-.078. And when I removed the gas block I could see the burn ring. Block was against shoulder and top of burn ring closer to barrel port but not overlapping. In each case the gas block was a no name leaky piece of junk.

 

[IndyIN]

that's exactly what it was. I only mentioned the tube/key interface since most of the time a loose block walks backwards, not forwards. (of course, there's lots of variables there in ammo and gun setup. but the bolt hitting forward is a sharper impulse than the recoil pushing the gun back). so long as the tube and the key look ok, I wouldn't worry about it. It may have just been they weren't aligned all that well.

make sure the block is centered left/right. put a 0.030 gap (about 1/32") between the block and the barrel "shoulder," tighten down good, and it should run. if it still gives you problems, I'd send it back (have them pin it if it's a clamp on, or add a dimple if it uses set screws).
I'd loosen it up first and take some brake cleaner and get as much of that oil off between the barrel and block as you can.

once you have the gas block tight, slide the carrier into the upper and see how smoothly the tube enters the key. very slight bends, usually just in the section outside the upper, can help things line up inside the upper. you don't want to really feel the key/tube hit, just a little resistance.

-rvb

i think I have it all squared away now. Plan on taking it to the range this weekend to see if it holds. It annoys me a little that it slid forward and scratched things up a little, so if I have more problems I'm going to get it fully taken care of.

 

[rvb]

i think I have it all squared away now. Plan on taking it to the range this weekend to see if it holds. It annoys me a little that it slid forward and scratched things up a little, so if I have more problems I'm going to get it fully taken care of.

curious, you never said if it was a clamp on style or has set screws? agree w/ the poster above about dimpling if it's set screws...

-rvb

 

[IndyIN]

curious, you never said if it was a clamp on style or has set screws? agree w/ the poster above about dimpling if it's set screws...

-rvb

It has set screws, just cleaned/ tightened up for now. I'm hesitant to do much more right now if I end up sending it back. It shouldn't matter for the warranty, but that would be my luck.

 

[rvb]

at least put some locktite on?

 

[IndyIN]

Yes, blue. If it doesn't hold I'll go to plan b.

 

[sig1473]

Yes, blue. If it doesn't hold I'll go to plan b.

I would use red loctite.