Have a red dot sight that I occasionally use on my MP15-22. Just bought a "real" MP15 with MBUS sights and the front sight blocks the red dot when mounted on the rail. On the 22 the front sight simply thumbscrews off. On the 15 it looks like 2 small pins need to be punched out and then the suppressor screwed off to slide it off the barrel. Is this correct or am I missing something? Are there ways to mounts DOT sights to rail without front sight removal. thx for any info.