Gunsmithing AR10 Gas Port Sizes?

[newguy2k3v2]

I have an Armalite Sass that I've been having accuracy issues with. Ive tried a few different things but the only one that's helped isturning the gas off and shooting it like a bolt gun.

It's a 20" barrel with a rifle gas system and 2 position gas block. From what I've gathered the port should be about .084". I pulled the block apart and a .092" fits loosely in the unsuppressed port in the cylinder and I'm pretty sure the hole in the barrel is larger yet. I need to get more drill bits to figure the exact sizes for everything.

I'm going to flip the port cylinder 180 and redrill my own ports. Any suggestions on what sizes to start at?

 

[ORD]

Re: AR10 Gas Port Sizes?

Middle of page 4, under "IV. Installation of Selective Gas System Components":

http://www.armalite.com/images/Tech%20No...8%20Rev%205.pdf

 

[newguy2k3v2]

Re: AR10 Gas Port Sizes?

Ok well that is the size that Armalite has the port in the barrel and my is probably close to that. The unsuppressed port in the gas block a .092" bit is loose in. I can't remember exactly right now but my buffer is ~13oz now and it's still slamming it pretty hard.

 

[Jumper]

Re: AR10 Gas Port Sizes?

The gas port size on my AR10-T was .085". Like you, I had to restrict the gas to get better accuracy. I had a carrier weight system installed but eventually I removed it and made my own adjustable gas block. Its 1MOA at 100yds with 168gr FGGM. Acceptable, but nothing to write home about.

 

[newguy2k3v2]

Re: AR10 Gas Port Sizes?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Jumper</div><div class="ubbcode-body">The gas port size on my AR10-T was .085". Like you, I had to restrict the gas to get better accuracy. I had a carrier weight system installed but eventually I removed it and made my own adjustable gas block. Its 1MOA at 100yds with 168gr FGGM. Acceptable, but nothing to write home about. </div></div>

If I can consistently get moa I'll be thrilled. Right now the only way it's achievable is if I turn the gas off, which kind of defeats the purpose.

I'm debating on wether or not to drill my own holes in the factory gas block cylinder as I haven't gotten an answer back from Armalite if they will sell me the cylinder only in case I do more harm than good.

I emailed PRI and they got back to me that they have .875 lopro adjustable gas blocks available now but they are a week or so out on the gas tubes for them. So I may go that route.

We'll see.

 

[newguy2k3v2]

Re: AR10 Gas Port Sizes?

I went ahead and drilled a new unsuppressed port in the gas block yesterday and dropped the buffer weight back down to normal weight.

I drilled it at .078" which I was under the impression wouldn't cycle the gun but it did just fine with 175 FGMM. I didn't have a very good position to shoot accurately from but I shot a group at 100yds that is as good as the gun has ever shot and recoil is WAY down.

Success so far.