[john kilgore]

Your'e belling the case way-way too much as a result of over sizing the brass.

You didn't state what dies your'e using and it dosen't much matter. Most dies provide for excessive sizing of 9mm brass because of problems in the 70's and 80's with a lot of "under-spec." forigen made reloadable brass available. Most quality 9mm brass if much better now with the surge in popularity of the 9mm in the late 80's and early 90's. (as well as ammo)
I had the same thing occuring to me loading for 9mm. I spent a great deal of time sorting out the problem as I needed absolute top grade match 9mm's for competition.
(As long as the ammo chambers freely, it should be okay, but will have poor-erratic accuracy.)
My fix was:
1. Size the case initially and decap only sizing the case enough to have adequate neck tension to properly hold the bullet after seating. (about the first 1/4"-1/3" back from the neck)
2. Only expand the neck the very minimum to allow seating of the bullet without scraping or deforming the bullet. This means approximately an additional 1/2 turn of the die for a cast bullet than a jacketed/plated.
3. After seating the bullet, I use a Lee "factory crimp die" to crimp (slight -taper crimp) and remove (smooth) the expanded base of the case to original factory diminsions-this allows all ammo to chamber reliably through all three of my 9mm's.
This results in "very low" to "no" run-out and with premium bullets and proper powder charges, accuracy equivalent to the very best factory ammo.