Most rifle sizing dies, if set up so the shellholder touches the base of the die, will over size the case, causing headspace problems. You don't specify what kind of dents you're getting, but I'm guessing there is too much case lube in the area of the shoulder. If that's not the case, then you're setting the shoulder back too far and you're looking at case head separations in the very near future. If the problem is too much lube, then wipe off any lube in the area of the shoulder and clean out your sizing die of excess lube, then try it again.
It would be a rare RCBS sizing die that was built wrong, but it could happen.
To properly set up your sizing die, take a case that the bolt of your rifle closes on with some slight resistance. Unscrew your sizing die about one full turn and size the case. Put the empty case in the rifle and see if the bolt still closes with that same slight resistance. If it does, screw the sizing die down about 1/4 turn and repeat the sizing/bolt fit process again. Keep doing this until the bolt will close with little to no resistance.
This sets the die up for the chamber of your rifle. Ideally, you'll want to set the shoulder back about .002" to .003", but no more than that. If you do, you'll over stretch the case upon firing and end up with the front portion stuck in the chamber and the rear portion will come out with the bolt.
Hope this helps.
Fred