A while back I was asking about the standard 1/2 x 28 birdcage flash hider and the 5/8 x 24 birdcage since I wanted to know if the M7 bayonet would work on the 30 caliber birdcage. Well, yes it does. My military surplus M7 bayonet arrived today and fits just fine on the 7.62 x 39.