Re: DPMS .308 / 7.62 Sportical Quad Rail
I am looking for a rifle length free float rail myself. So far here are the options I have found (with estimated retail prices):
Yankee Hill - $175
Daniel Defense Lite - $375
Troy 13.8" rail - $335
Knight's Armament - URX or SR25 rail - $400
Badger (not a true quad rail) - $175
JP/VTac - see above
Precision Reflex (SPR type) - $340
I am sure I forgot some, but it's a start.
If you just wanted to do a free float tube, I would get a standard DPMS tube. I am sure you can find a used one for about $40-$50. If you are going to use a rifle length rail/tube(which I recommend) you will need a low profile gas block with the Sportical.