My 2 friends have built the exakt same ar15 but one of the rifles dont work correctly. When we went to the range he loaded the magazine and put it in the ar15 and pulled the charging handle and fired the first shoot and then he tryed to fire the second round but the rifles just clicks. The hammer is cocked back and falls when i he pulls the trigger but its no new case in the chamber, im not even sure if it trows the old case out. Here is what we have tryed; Changed the gasblock/gastube, BCG, magazine and i think they have changed the lower to. I dont understand whats cusing this, i belived it was a gas issue but now i dont think that anymore. The only gas problem it can be is the gas port but would the hammer cock back without any gas? If the fired case is stuck it should be the extractor or can it be anything else? I think it trows the old case out but im not sure. If you have any idea how to solve this please tell me, even if you are not sure but think something can solve it. I would appreciate it Wanna kill these ads? We can help!