My experience with aluminum gas blocks dates back to 2002, when the first carbine I ever saw and shot with one was the DPMS Lo-pro AR15 that a buddy of mine owned. We burned through a lot of high volume sessions with that gun, and the gas block basically expanded faster than the steel, leading to gas leakage and short-stroking. It had a Carbine-Length Gas System (CLGS). I had never seen this before shooting boat loads of 5.56 through military guns with steel FSB's, to include a lot of automatic fire in both rifles and carbines.
I did an experiment once with a 7075 T6 Brownell's aluminum gas block on a Mid-Length Gas System AR15 carbine, and even went to the extent to seal the gas block to the barrel with a metal epoxy. Same thing happened-short stroking, especially in cold weather. I had to cut that block off, that's how well it was mated to the barrel.
You can get away with it on RLGS, since the pressure is much lower up there, but it has to be made right by someone that knows what they are doing, like JP.
I personally only use steel gas block, fitted tightly and sealed, with the ports aligned CTC, not just thrown on there like we're seeing happen a lot with the attention deficit generation.
Coefficient of thermal expansion ratio between aluminum and steel works against you on CLGS and MLGS in the AR15. Stick to steel.


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