I had to set a lighter spring in my total sized M16 A2 clone nevertheless it ran high-quality. Experimented with again With all the 11.5" Comando Colt upper. No dice. Ran 500 rounds of wolf by it these days. Didnt damage the spring in the least. Reference listing entries without https://arthurqjapi.wikigop.com/1613290/not_known_factual_statements_about_frt