I have a Bushmaster 16" barreled M4-gery. I have not had any problem using the carry handle and front sight to zero at 50 yards. I bought a GG&G A-2 flip up BUIS to mount under optics, and cannot get it to zero at 50 yards. I bought and installed Bushmaster's higher front sight, but at the top of its elevation, I am still 3"high at 50 yards. Any suggestions?
Also, who makes a same plane A-2 apeture?