Bwana-be,
I've been after Pottsy to get a decent camera for quite awhile. What Martin says about rolling or peeling down the inside surface of the jacket works. I discovered it by accident. I believe there is another way to create a partition. It requires a section of copper tubing the length you want, and placing it in a die. A tight fitting punch then presses one end of the tubing, with enough force to get the center of the jacket to buckle inwards, forming the partition. I'd email Richard Corbin for the exact procedure. Placing another jacket, that is inverted,inside a larger one may be another avenue to explore. Once you get started with swaging you'll find there is no end in what you can try. The only limitation is the tooling, and that can be over come with imagination and, what else, new tools.

Jungli Bains
Is right you can use a sec/ jacket to make a partion
it just make for an expencive bullet two jacket's cost in large bore about 14 cent's a pop .Maybe i am being a bit tight fisted....

You're right about the somewhat higher cost using two cups, but I was just pointing out there is more than one way to skin a cat in swaging.