Thanks, Mike,

The .375 you mention is one of the calibers I found interesting. The bbl is not suitable for a rebore, due to it's rather stubby length.

Sooo...wors' cometa wors', and I don't turn up a nifty donor exotic, one of the mass bbl makers has ready to go, pre-chambered .303's for about two hundred. -- or did last time I checked. They do need a final fit for headspace.

Before doing that, tho, I think an extended cyber-fishing trip for the desiderata maybe in order. I'm pretty sure that this forum is the place to start. ;~`)

Relax; we're all experts here.