So here was my last build... ... And the new!!! i picked this up for 300$ off a buddy who needed $$ it has MOE grip CTR stock LaRue Billet Stealth Upper M&P Lower CMMG LPK Magpul Trigger Housing Tango Down QD Front Grip XTM rail covers 3 Pmags a 5.11 Tact Carry Bag So pretty sure all i need is the gas system.. barrel.. Rails If im not correct ive never really built a upper lol.. What would you guys do? i plan to run optics.. Fixed front site? Flip up front site? just wanting some input Thanks guys!