bko 03 zenitram asa, tickler lpr, ergo reg, vapor blot, j&j 2 pc barrel, aka mity max,
stops blow back
helps air efficiency a little
if you have blow back get this bolt it will get rid of it.also the bolt fits good in the gun because off the o rings on it. also i think that it is nice that this bolt is not delron so that way you don't have to worry about it swelling.
if you have blow back on your bushmaster get this bolt you will be very happy