I used to use a primging arm on my Rockchucker all the time. I got tired of changing primer plugs, so now I use the Rockchucker for large primers and a Lee hand tool for small ones.
I have owned a Rock chucker for over 25 years and at first I did use the primer tool until a friend showed me the advantage of the Lee auto prime.
What I like about it is once your brass is through sizing and belling you can (and I have) set in front of the TV and spent hours priming brass. There are several companies that make primer tools like the Lee but for over all price and quality they are hard to beat.
