I had to place a lighter spring in my whole sized M16 A2 clone however it ran great. Tried using again with the eleven.five" Comando Colt upper. No dice. Ran 500 rounds of wolf as a result of it today. Didnt hurt the spring in any respect. - Involves optimized https://zanderlbtbf.gigswiki.com/5811421/fascination_about_rare_breed_trigger