I have a KAC M5 RAS I want to use and really don't see the point of a 20" rifle anymore unless I step up to something like 6.5. Everybody preaches free float but in the real world would a decent Grendel upper with a M5 and Bipod be accurate enough to be a hunting rifle? 2 legged critters really only need minute of bad guy so I'm not worried there, just clean shots on white tails out to 300ish.
Non-freefloating doesn't decrease accuracy. It just means that your POI can shift depending on how much weight/pressure is on the RAS from one point to another.
I personally would not have any problem using the M5 RAS for this application.
It may impact different when prone with the bipod and when off hand so just check your zero in multiple positions.