Would you trade a sig 716 patrol 308 for a keltec rfb 308  ?   Just wondering

Negative

Not likely.

I have owned both. I sold the RFB first and just recently sold the Sig P716 Patrol rifle. The Sig P716 is a better rifle than the RFB. And my SCAR 17 rifle is better than both of them. It is a lot lighter, a lot more accurate, and has a lot less recoil (even though it is a lot lighter). I also purchased a Stryker Industries S.E.A.L. which is an aluminum lower receiver to replace the polymer FN receiver and in my case I purchased the SEAL that was made to use MagPul SR25 Pmags 25rd magazines. I now have the option to use the original FN lower and it's FN magazines or switch to the SEAL and use 25rd Pmags.

FWIW I wouldn't give my RFB in exchange for a SIG716....

I very much like the concept of the RFB, but have been more tempered on the reality.  RFB reliability and longevity issues appear to at best, be spotty.  It's a roll of the dice on if you get a good one.

OP: Definitely make sure it's a Gen2 RFB - gas adjustment is the easiest thing to look at.  Gen1 adjusts with a case rim (big half-circle notches) while Gen2 adjusts with a bullet point (small circular cutouts).