so my sniper wont work with upgrades..

So a while back I put in the internals from my tm precision hopup and inner barrel into my well mb07 hopup shell with a king arms bucking and it fit correctly into the shell but it wont fire. Its really wierd cocking it and it almost feels like its catching something when pushing the bolt forward. Does anyone know what could have happened or what the problem is? I feel like im really having bad luck with snipers lately.