Only if you're using a Choate extension
Seriously folks, the S&J is just fine. If you need to flare/straighten/smooth the end of a magazine tube a common brass plumb will do the trick.
I've said it before and I'll say it again: the S&J extension is a work of art, but throw away the spring and follower that comes with it. The total spring diameter is too small, the weight is way too much and the mediocre follower requires the use of their spring. Re-use your old factory follower (strong, light, and most importantly rounded edges) and factory extended spring.