Found a pretty good A2 birdcage flash hider on Thingiverse, but it doesn't actually seem to have the correct threading, so I edited it and added the 14mm CCW (M14x1 LH) threading that's on most airsoft replicas you would want to put an A2 birdcage on to begin with.
Recommended settings:
Would probably print with something heat and UV resistant like PETG, ASA, ABS, etc. Not PLA. Impact resistance would probably be good as well.
The author remixed this model.
Added proper 14mm CCW (M14x1 LH) threading.