Cotton Arms Adjustable Gas Block - .750"
This Cotton Arms Adjustable Gas Block is precision machined for AR-15/M4 pattern firearms. The end of the adjustment screw pocket is deliberately left unfinished on the last ½ turn. Upon adjustment, this unfinished half turn imparts a bite, eliminating the need for applying thread locker or gimmicky mechanisms.
- Precision machined
- 4140 chrome moly steel
- Black oxide 5/64 Allen head set screw
- 0.309” 3/32” Allen head adjustment screw
- Inner diameter: 0.752”
- Wall thickness: 0.1615”
- Length: 1”
- Height: 1.345”
- Gas port diameter: 0.181”
Ratings & Reviews
by Josh -
Bought this due to price. Installed it and it quite literally blew up on the first shot. The adjustment was at approximately 3\4 open and it was on a pistol length system firing 55gr M193.
<br>From PA: Very sorry to hear this! One of our reps will contact you.
Cheap but it simply worked for me
by Chris -
After seeing the posted review I got nervous as I hadn't shot my rifle with this block on it since finishing the build several months ago. Didn't need to worry. I am running a lightweight BCG, and 1oz recoil system so the block was adjusted to be barely open and I had no issues. After the first 20 shots had to open a little more to account for build up but otherwise worked perfect. The no set screw wasn't an issue as my dialed in setting stayed out and didn't walk out. For the money it'll do the job.
by GARY -
This block feels solid and durable. However, upon installation I noticed some burrs inside the block that hindered a smooth transition into the barrel. Once this was mitigated, I installed the set screw for gas regulation. The screw stopped as soon as it hit the threads. I felt like I was going to strip it out as I torqued down on this stainless colored screw. Luckily I was to push the gritty threads alone and seat the set screw properly. This is a decent buy however only if it is on sale. My rifle appears to be firing flawlessly as I am using a lightweight bcg. With 200 rounds down range and hopefully more to come.
Solid piece of junk.
I wound up with one of these (not purchased from PA), and feel compelled to write a review here after seeing it offered. This GB fit so tight, it had to be tapped on to get it to seat properly, this after de-burring it inside. The gas tube was difficult to insert, and the roll pin hole was mis-aligned, preventing the pin from passing cleanly through. I would not recommend this item to anyone.
Good design, bad QC
by 4thbox -
First one of these was incorrectly manufactured, the roll pin hole and adjustment screw hole were in the wrong place as if the block was placed in the jig to drill those hole backwards or something. I exchanged it with Primary Arms and the new one is well made.
<br>This method of adjustment retention is a good low tech solution that is easy to adjust and easy to clean should it ever seize up from fouling. I have some pricey detent-style examples that I'd honestly trade out for these if I could get this in a melonite finish.
Small budget option
by Xfrog1107 -
Installed for someone who purchased due to price. This is the simple way to close your GP. It works and should do fine for a hunting or range gun. Pros - cost... Cons - HEAVY, needs to be driven or pressed on. No set screw to bind the adjustment screw. Use of lock tite is mandatory so make sure it is set correctly the first time.