Badgeredd, where did you have your Contender barrels done? Are those stubs you've done yourself?
I'm interested in doing up a Contender carbine barrel. At first I was looking at doing a 22 TCM rimmed on 38 Spl brass since I have thousands of them. I made a few dummies and after annealing the top 3/8" I got brass to form nicely just running them up into the TCM die.
But after reading about your cartridge I think I like the 30 Cal idea better. I intend this as a cast boolit gun anyway, and 30 cals are much easier to cast, plus I already have a bunch of molds.