Cartridge case deflector enables quick operation in both of those right and remaining handed shooting positions for amplified tactical apps It's an ordinary FSB and no I had no issues sighting it in. I initially created it which has a DPMS A2 upper receiver just before obtaining the 604 receiver. https://devinitdqy.idblogmaker.com/26359590/top-guidelines-of-colt-10-5-inch-9mm-smg-upper-receiver-assembly