SMG has some rifle length aluminum free floated quad rails for $53 and change for members.
enter discount code "SK669" for double discount TODAY ONLY. 9-19-2012
i think the shipped price is like $58
i don't know if these are any good but SMG is good for a refund if their crap.
i suspect their the same make as the ones amazon sells, which i have a middy that is really nice for the low $$.
i went ahead and got some of the rifle ones --i am sure i can put them on something i got laying around--
enter code for the rails if ya can't find them -- # a2a-209767
the trend of the ninjas it to put the rifle FF-quads over the gas block and make the rifle "all-rails"
these should look pretty good on one of my 18" set up that way---
Sportsman's Guide - Discount Hunting Gear, Discount Hunting Boots, Discount Shoes, Discount Ammunition, Discount Ammo, Discount Boots, Military Surplus, Outdoor Gear at The Sportsman's Guide
i rarely plug the SMG as i have had to return a lot of shit. but they do make a nice deal sometimes.