hi can any one shed any light on this AR-15 build?, I've just run into a problem with my shorty AR-15 build, I first put it together as a .22 rifle for my daughter, used a well know convertion kit and all works OK! last week decided to get a .223 bolt so put it in and tried with blanks and a BFA all worked OK! then put in factory rounds, they racked and chambered OK, fired and ejected OK, loaded the next round but the hammer did not lock back? racked it back, which ejected the live round, put a new in and locked the hammer???? any body know whats going on????