Re: 7mm WSM Dies
You are getting really good advice from these experts. Heed it well. The Redding bushing dies are like the Cadillac of the industry, while the RCBS are like a Ford Pickup.
If you must use RCBS, add an "O" ring between the die body and the nut holding the de-capping stem. That lets the stem "float" so the brass can find it's natural center. I personally have replaced the de-capping stem setups in my RCBS dies with a product sold by Hornady. It includes the stem, a de-capping pin, a floating carbide expander button, and a tear-drop shaped expander button (really good for necking brass up or down.)
Another alternative for you is the Forster seating die (as well as the seater die). I've found them to be much better than the RCBS (engineering wise) but still not quite up to the Redding (manufacturing wise). My personal 7WSM set up switched over from RCBS to Forster several years ago. My groups shrank, and I've been very happy with the set up. I should mention that I use a Redding body die with the Forster set. It seems to work together well.
Whatever you do, have fun and shoot straight.