re: I come to my OB brethren in seek of wise guidance (AR15 BUILD)

I did the exact same thing with a BCM upper on my build.

The front site isnt that hard, just need to grind it off while being careful not to gouge the barrel.

Taking the barrel nut off however can prove to be difficult as BCM really torque's those things down. I tried to go the cheap route and just wedge the upper between two blocks of wood and by the time I broke nut loose I cracked the upper housing. So then I had to buy a replacement upper + the upper block vise to hold it properly.