I’m a little embarrassed to admit this, but I never gave an adjustable gas block on an AR-15 much thought until I was forced to use one recently while evaluating an ArmaLite M-15 VSR Versatile Sporting Rifle. I’m not talking about the three-position blocks like on a Ruger. I’m talking about the ones that you fully close and then slowly open until you get 100 percent reliability. Thoughtlessly I had dismissed them as one of those superfluous gizzies manufacturers added to have some feature—anything—to help separate their AR-15 from all the others on the market. I was wrong—really, really wrong.
Everything I had read indicated an adjustable block lets you “tune” the gun to your load or a suppressor. Hey, if I wasn’t using a suppressor and the gun was running, what needed tuning?
On the ArmaLite, the company recommends first closing the gas block adjustment fully and then opening it 2 1/2 turns. Next, you simply load one round in the magazine and fire it. If the bolt does not lock back when you shoot, turn the adjustment screw counterclockwise another 1/4 turn and repeat until the bolt consistently locks back.
ArmaLite recommends an additional 1/4 counterclockwise turn to ensure reliability. With Hornady’s .223 Rem. Superformance load, I was open 3 1/4 turns before tightening the setscrew. Every other load I shot cycled equally well at that setting, so that is where I left it. I was impressed with how much a difference tuning the gas block makes. Instead of simply tuning to the load, it reduces gun movement caused by recoil—a lot. It’s almost like having a muzzle brake without the added blast.
“Shooting Guns & Having Fun”
In 2008, Mayer returned to the editorial side of publishing, this time in the digital field, as Editorial Director for Guns & Ammo, Shooting Times, Handguns and Rifleshooter online magazines. After a brief stint in 2011 as the Digital Media Director for an ABC TV affiliate, Mayer returned to the outdoors industry and Safari Club International where he is currently Assistant Publisher and Multi-Media Communications Editor.