Optics Planet has some Aero Precision parts on sale, so I snagged an M5 upper receiver and an M5 Atlas handguard. Looking to build a .308/7.62 carbine. Undecided on barrel length. This will not be a long range rig, so on the short side, but not SBR. Looks like at least some 16 in. barrels have a 1:11.25 twist, don't think I want that, so leaning towards an 18 in. barrel with a 1:10 in. twist. I certainly have a while to contemplate all the other components.