Im pretty sure real firearms are mostly used still. All fire blanks, blowback operated dont need a BFA, gas operated either have the BFA and overlayed effects, or (if available) use blanks with plastic bullets that burn up in the air almost instantly, travel just enough to allow the gun to cycle properly (such as 5.45x39 blanks). Im sure a a BFA with a small hole on it to allow the flame to escape, combined with a lighter bolt/recoil spring may allow enough pressure for cycling...
Edit: here are the blanks with the plastic bullets I speak of:
Very reasonable prices IMO!