Title says it all. I'm ordering a KAC RIS or KAC RAS tonight from MSTN. Which do you think is better and why? Thanks for your time and I look forward to reading some quality responses.

RAS is more secure, but it might not fit on your barrel.

If you get a RAS I suggest getting one with the lower half that engages the barrel nut. Much more secure than the ones that are just held by the delta ring. Got one from Denny's and very happy with it.

Editted to add- the RAS' top piece has a clamp to tighten it to the barrel nut, the RIS doesn't.

Quoted: If you get a RAS I suggest getting one with the lower half that engages the barrel nut. Much more secure than the ones that are just held by the delta ring. Got one from Denny's and very happy with it. Editted to add- the RAS' top piece has a clamp to tighten it to the barrel nut, the RIS doesn't.

Have you actually had a poor experience with the non-clamping lower half?  I use a VFG on mine (doesn't clamp) and I've never had any problems with it shifting, wobbling, etc.  I use the VFG exclusively.

The RAS is more secure in that it locks to the barrel nut while the RIS locks to the handguard cap.  If you can swing the $120, get the locking lower rail.  If not, you shouldn't have any issues with your lower rail unless your carbine is going to see some hard use.  FYI, though, the locking lower rails can be tough to get at times so you might want to spring for it now in case you decide you want it later.

Have you actually had a poor experience with the non-clamping lower half?  I use a VFG on mine (doesn't clamp) and I've never had any problems with it shifting, wobbling, etc.  I use the VFG exclusively.Gimme_A_Carbine

I had the standard RAS years ago and had some wiggle with the VFG. Switched to the RAS II and got spoiled. On a different carbine I wanted an EOTech, which isn't compatible with the II so I got the improved RAS from Denny's. $309 with the bottom  locking piece. Now all is right in the world. The lower pieces usually are a $120 item by themselves so I was quite happy with the price. Don't get me wrong, the regular RAS is a great piece of gear but the upgrade after selling my rail system was only about $20 so I jumped on it.