I would like to enquire if any of the members have experience in fireforming .17 Fireball, after having some new stock .221 through forming dies, the cases exhibit a slightly de formed area just below the start of the shoulder curvature, which even though small it will reduce case volume, & as these small charge cases are sensitive, to small incremental charge weight changes, I thought I should ask here?

I used the regular loads and never had any problems. Formed with Redding form die, then full length resized, and they shot just fine.

The slight ring where the old neck/shoulder junction of the .221 brass was represents no problem. It will iron out on the first shot.

What might be a problem is the possibility of the neck walls being too thick. If your loaded round chambers easily this indicates the neck walls are not excessively thick for your chamber. If you want assurance of this, then black a couple of necks with soot from a candle and carefully chamber and withdraw them to see if there is significant friction (as indicated by scraping of the soot) between the neck and the chamber wall.

With a .17 caliber the old "test" of seeing if a bullet will re-enter the mouth of a fired case isn't a valid one. The tiny .17 neck springs back enough that it will grip the bullet even if the neck walls are plenty thin enough for the chamber.

All chamber nicely, I have loaded them up with 30 grain Berger HP's, with some start weights & a few laddering upwards, might get out with them soon.