A couple of friends dropped by . This is the beginning of the basic problem of wanting an AR. These are just basic cosmetic variations. The damned things are worse than that Contender/Encore that you innocently checked out .
Attachment 169487
Now you have 6 bbls , 2 receivers ,stocks .
The AR starts with 5 basic configurations then you have 10 basic butt stocks , dozens of fore ends , dozens of gas blocks from GI to 4 plex 1913 and just a collar. Gas ports come in carbine, mid and rifle length and pistol . Barrels run from 6-24", from .9 to the .825 gas port step to a GI with a M203 step, with and without threads for 50 or more flash hiders .
Cartridges ! Good greif there are 4 or 5 bolt faces for basically every case head . If it has less than a 2.3 OAL and is of a caliber from 17-50 and rimless without a belt from the mundane 223 to a shortened 250 Savage that on paper looks like a 257 Roberts . There are straight blow back uppers available for 9,40 and 45.