The CTR picture above is the bare minimum I would use ( I usually replace all the stock buttstocks of my AR carbines with this due to the lock key which grips the tube and eliminates wobble)--but keep in mind your changing the "dynamics" of your weapon to a carbine style stock from a sniper system if going with this kind of stock--I'd stick with the PRS or equivalent. My LRT SASS has one and it's an amazing tack-driver; never fired any weapon that spits accuracy no matter what you feed it like it.