stainless is not good for rapid fire, and they are generally more expensive.
you need 16" length for a bbl to be legal with out a SBR registration
nobody makes that I know of 14" bbls. there are 14.5" bbls though, and you would need to perm attach a brake or flash suppressor
also you got those funny looks from the other guy because a 65gr bullet is not light, that is a heavier 5.56 round, light is like a 4ogr varmint bullet.
you sound like your more interested in looking cool than having a functional rifle, no offence you may want to reconsider what you thinkis important. Don't get me wrong, I like to have my guns look cool too, but not ever at the expense of function, cool factor is low on the priority list.