I would stay away from the bushmaster kaboom 15 i mean carbon 15
you see them blown up quite often over at AR15.com
i built my AR pistol with a DPMS kitty kat upper 7.5 inch barrel chrome lined 1/9 twist
i have a noveske brake on it which tames it alot. i have a YHM 4 rail hand guard STD front sight, DPMS rear sight and a superior arms "pistol only" lower.