Here is an exerpt from an article on the Zipper...
I wrote an article on the 219 Zipper several years ago and included how I made 219 brass from 30-30. Here it is....
Glenn
The cases were very lightly lubed and run into a 32-40 Winchester sizing die. This slimmed down the shoulder, and left the neck at .30 caliber. Then the brass was sized again using a 25-35 Winchester die which added the bottleneck and reduced the neck to .25 caliber. The final sizing utilized a 219 Zipper full-length sizing die and produced a 219 Zipper case with an elongated neck. This sizing operation took a little extra time because of the amount of brass that had to be reshaped. First the case was sized about the length of the neck. The case was removed from the die and the ring of lube that had formed at the base of the neck was wiped away to prevent wrinkles in the shoulder during the full-length sizing. Then the case was run back in the die and full-length sized. Finally the excessive neck length was removed and the cases were trimmed to length. The 30-30 cases had been worked pretty heavily and the brass in the neck had thickened, so neck-turning would be required. After turning the necks the flash holes were de-burred and the necks chamfered, both inside and out. The brass was full-length sized again, this time with the shell holder pressing against the bottom of the sizing die, which gives a slight “cam” effect when the shell holder touches the bottom of the die.