This is actually a pistol and not a rifle, and yet I was worried that my fellow 1911 smiths might skin me if I put it in with the custom 1911's!
About a year ago I took a customer's AR-15 pistol and changed it over to .300 AAC Blackout. Used an Armalite SPR-1 monolithic upper and a Satern barrel.... it worked and shot very well.
I asked him to send it back recently to put an adjustable gas block on it-- I got a few from Paladin Machine and I thought they were very nicely made so I thought his BLK might be a good place to try one out.
Barrel with gasblock installed. It is made with two 10-32 set screws to hold it on the barrel-- as is my practice I used them to hold the thing in place while I drilled for a cross pin. Same deal with the gas tube-- the instructions are cut .900 off it and then it's held in the block with two set screws. I put two .078 roll pins in place to make sure it stayed put when the screws come loose. The rotating adjustment shaft is held in place with a snap ring. The whole thing is heat treated but is on the 'tough" side rather than the "rock hard" side, so I was able to take a little weight out of it-- maybe 1/2 ounce, big deal. It is not heavy to begin with. I had to do a lot of machining and fiddling with the Armalite unit to make room for the gas block-- it is a little larger than the lo-pro unit I had used originally.
Close up of it all together.
The muzzle device is a simple cone flash hider made out of titanium. I took one web out of the rail for access to the adjustment. Worked out about right, you can get to it but it doesn't stick out anywhere.