Pensacola Joe
Expert
My experience is it is impossible to double charge a 223. You may get a tiny bit more in but like you said , using proper rifle powder, it won’t happen.More than likely, the hammer dropped while the bolt is not fully in battery i.e did not chamber the round completely. Test it with your UNLOADED AR, retract the bolt enough and pull the trigger. Its hard to double charge a .223 with the proper powder.