Regarding forming .22 High Power.. I have an RCBS 30-30 to .22 HP case forming die set that consists of three case forming dies and following the last die (ID of 0.255) the RCBS instructions then have you run the case into a .22 HP full length sizing die.
I would expect that forming the .219 Zipper Imp. would be similar. The only downside I know is the cost of the three die case forming die set.
Good luck in your project.
As an oh-by-the-way statement, many years ago Bob Milek recommended the use of Alberto VO5 hair dressing for case forming lube on the .30 Herrett cases. I tried it and it worked just like Bob said it would. I am on my second tube of the stuff starting with my first .30 Herrett and I still use it for case forming...
