Beretta M92 won't shoot

[Balzerk07]

My problem is this, I put the magazine in the gun, pull the trigger for nothing to happen. The magazine is filled with gas and bb's, what kind of gas? Good ol' Propane. I haven't had a problem yet with it. When I look carefully at the valve knocker, it looks as though its hitting the wrong part of the magazine. But the hammer assembly is flawless and I can't do anything to change it. I might add it did work before I replaced the trigger spring. Any suggestions would be appreciated greatly.