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.
“This Gilboa APR appears to be a 5.56 NATO rifle. The muzzle blast must be fierce from that combination of short barrel and standard flash suppressor.”
Pah, muzzle flash would be piker compared to a 7.62x54 MN carbine, now there is a muzzle flash.
http://www.youtube.com/watch?v=I-YOgEr5Qho