I remember looking at the nice Pictinny rails for my AR, only to be dissapointed in the price. I could do more with $200 than just add that little bit. But I found a great deal. Ebay had some folks that sell these at a very low cost.
Google carbine length quad rail, and you can find them under $30 delivered.



I have desert grips and stock, so I searched for one in dark earth. Low and behold, for about 7 dollars more, they had that too.

These rails give opportunities to mount some cool accessories on your weapon. From laser sights to flashlight holders and hand grips. There is even a hand grip with a bi-pod built in. Anyway, just wanted to share my good fortune

the only thing i would be nervous about is the tolerances and durability of the rails.
last thing i would want is something to come apart on me.

If you're going to buy free float rails the cheapest I would go with is Yankee Hill Machine or YHM.