is that a .223 cal?
Many moons ago I had a chance to shoot a 10-inch barrel XM177E1 “shorty”. In bright daylight, the fireball was about three feet — and that was with a standard flash suppressor.
Colt designed a special “sound and flash moderator” to go on these cut-down M16 rifles that was VERY effective. However, this particular rifle had its special S&F moderator removed and replaced with a standard M16 flash suppressor. The operator said it was very dramatic to shoot at night and tended to draw a lot of return fire.