Well went shooting today on my grandpas farm and shot a R15 with the stainless barrel and it was nice. His friend had just got it and brought it over. It was nice although little goofy looking with the triangle barrel end.   I don't want to spend 1200+ dollars for a plinker lol.  O already have a spikes 16in upper and its awesome but looking for something different more than anything. Any problems with switching bolt carrier between uppers?  How about differences in 18-20in uppers?  Also undecided on tube hand guards or rails. Want a flat top and no regular front sight. Any thoughts and a LaRue upper isn't available to me at this point lol.

PKfirearms has several 18" configurations using Sabre SS barrels.  They come complete and you would not have to worry about switching BFG between your two uppers.