So, AR15 guru's...

[Dirty J]

It is perfectly straight, that I am sure of, but it is up tight against the shoulder. There is no gap. How can I tell if it needs a gap? How would one measure it? Remove the block and look at the carbon pattern around the hole in the barrel and see if it looks funny, or not in a perfect circle?

Remove it and measure... or check for a fouling circle. Either could work now that it’s been shot.

 

[Freshly Minted Georgian!]

DJ is right, I think officially the back edge of the block is supposed to be .030" off the barrel shoulder. You can check it with a feeler gauge or in a pinch, the wall of an aluminum can.

 

[BIGLEW]

One easy way to tell is to remove the barrel with the gas block and tube still attached. Use your finger to plug the end and blow into the chamber and see how the air flows. Then adjust the tube to see if the air becomes and easier flow. It could be off just a bit. And in no way do I mean any of that as sexual. LOL

 

[SirBannedAlot]

Buffer weight 2 7/8 ounces on my scale... so assuming it is 3oz

 

[gregmanz]

I would assume gas also. A typical ar can cycle .223, even weak Tula and Have yet to see one not cycle with an h3 buffer.


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[Bushwhacker]

Under gassed

 

[Dirty J]

Buffer weight 2 7/8 ounces on my scale... so assuming it is 3oz

Lol. If it’s short stroking on a sub 3oz buffer, there’s something up with the gas system for sure.

Check the block alignment first.

If that checks out.. move to the gas key.. check for looseness... fit between the gas tube and gas key..

Then gas rings on the bolt.

 

[SirBannedAlot]

Lol. If it’s short stroking on a sub 3oz buffer, there’s something up with the gas system for sure.

Check the block alignment first.

If that checks out.. move to the gas key.. check for looseness... fit between the gas tube and gas key..

Then gas rings on the bolt.

What should I look for on the gas rings? I see conflicting reports that the rings need to be spaced, while others have claimed that it doesn't matter and the gun should function with just one working gas ring...

I don't have the upper with me at the moment. I stopped by PNR Ammunition in Buford to look for a new gas block, and the guy there seemed knowledgeable and offered to look at it for me and said to come back in the morning. I figured I would research it, so that if he couldn't sort it, I can go and buy the appropriate parts or check things and see if I can get it working.

I have built many AR's but this is the first one I have had issues with.

 

[Allsmiles]

Do you have a can to put on it? If it cycles with can, its a gas issue. I had gun that would only run with can installed. Turns out gas block was drilled incorrectly and putting a new on solved the issue.

 

[SirBannedAlot]

Do you have a can to put on it? If it cycles with can, its a gas issue. I had gun that would only run with can installed. Turns out gas block was drilled incorrectly and putting a new on solved the issue.

I do not. But I will start with the gas block and see where that leads me.