Probably time to do a chamber cast. I'm surprised the Zipper case doesn't fit, but who knows.

I have one of Landis' books, although I'm not sure whether it's the one you need, and I'll try to find it. I also have an early book on wildcat cartridges and I'll check to see if there's a reference to this cartridge in that.

Having a cardiac catheterization procedure tomorrow morning, so I may not get back to you for a couple of days.