AR Adjustable gas blocks

[Matt Pitchon]

I'm curious. Who is using them? What has been your experience? Do they make a difference? How do you keep them in adjustment?

The little I've seen on them suggests they work, but are sensitive and can readily come out of adjustment. I have one on my match rifle, but have had to use JB Weld to keep it from moving. An adjustment change of 1/8 turn is the difference between cycling, not cycling, and over cycling. When carefully adjusted for a particular load, the recoil impulse is softer. I think what is happening is the bolt carrier is not slamming into the stops preventing the hammer impulse.

Just wondering what others have experienced.

 

[Larryh128]

Absolutely no experience with them BUT from what I've read & seen on some tactical shows, their main use is to create proper cycling with & without a suppressor attached.

 

[Jeff A]

I have two AR Uppers and have JP adjustable gas blocks on both. One is a .223 and the other is a 6.5 Grendel. No issues and they stay where they are set. I would not be without them.

 

[rminut]

Matt,
I had to close mine down some in order to use MR2000 in my AR and it worked well. I put some Loctite Red on the threads and it's held fine since.

 

[Scott Harris]

I tried a couple, ended up putting the non-adustables back on. This is a zero value add product in my opinion.

 

[Matt Pitchon]

I didn't need it until 2000MR and the 90s. With a standard port and block, the rims would show deformity as if it were trying to extract before the case had released. I think the best solution is a gas port two inches further out. But closing the existing port and re-drilling a new one is non trivial on an existing barrel.

I have the JP Block and the threads are so loose the screw backs out within a few shots without the JB Weld. I tried blue Loctite and it blew out. Maybe I have a poorly machined block.

 

[LRPV]

A company called Syrac builds an adjustable block that employs a clicker for positive stops (4 detents per 1 revolution) so that the adjustments cannot be moved. Seekins makes one that has a brass set screw that tightens down on the actual adjustment bolt. The Syrac works. I haven't had the Seekins long enough to tell for sure but I have no reasons to think it won't at this point.

Jason

 

[Matt Pitchon]

Jason:

Thanks. The Syrac sounds like the right ticket. I'll give it a try.

Matt

 

[rminut]

Matt,
I run one on a 6br spacegun so slowing the action speed down makes it easier on the expensive brass. The port is only one inch farther out so 2000MR was really slamming the carrier back. My block actually had a burr in it and wouldn't close down at first once I found that and fixed it I was able to find a sweet spot to run H4895 for 200/300 and 2000MR for 600.

I believe John Benjamin build adjustable blocks in Oregon if you can get a hold of him. I don't have contact info though