For anyone contemplating a build vs buy I'll give you the rundown on a rig I built for a guy I work with.
Midlength Cav Arms 16" upper: In case you didnt know the barrel is by Sabre defense and chrome lined 1/9. The steel is the same used for 50M2 barrels, very tough stuff. IMHO a step above bushmaster and possibly colts.
Stag lower, he overpaid for it about $30ish. I could have found him a better price.
DPMS LPK from brownells.
6 Position Cav Arms stock
ARMS #40A2 buis ( damned nice sight btw)
single point sling adapter
single point sling
Right at around $800 total.
Not considerably cheaper than you can buy a factory carbine for but in a configuration you cannot get. Midlength flattop with a very nice flip up buis and ready for optics.
I highly reccomend a build over buying factory. He could have saved a few bucks here and there but it's still not bad for a 100% new rifle.