just like Raven said....if your barrel is a mid length gas system a carbine gas tube will be too short..... look at all the hot gas marks in your chamber area. You must be able to have the bcg lock back on the last round...thats a major function check.....not locking back on the bolt catch will reveal problemos in the gas/recoil system. In the pic the gas tube looks to be halfway across the clam shell looking indent as it should be....she needs more lube fer sure.... Wash