I have several carbine length gas seystem AR uppers in 5.56 with A-2 sight towers
Tired of dented brass and 1 o'clock ejection I purchased a Ruber City Armory adjustable gas key and installed it on an M16 bolt
Simple instructions supplied with the key were simple/very easy to follow and after the 4th round the rifle ran the rest of the day without a single issue
Ejection is now 3 o'clock