is your barrel threaded 1/2x20 or 1/2x28 and the silencer you have doesnt match. 1) Barrel end threaded adapter female 1/2-20 UNF to male 1/2-28 UNF 2) Barrel end threaded adapter female 1/2-28 UNF to male 1/2-20 UNF Black alloy with knurling for non slip grip. Through bore is 8.20 Threads length 12mm Body OD 18.85mm