If I was having a custom single shot rifle made, such as a modified Ruger No1, a Dakota Model 10, or even a Winchester/Browning Hiwall,
I'd have it chambered in 7-30 Waters or 307 Winchester.
Something about a rimmed cartridge in a single shot rifle.
The way I figure it, it wouldn't be my primary gun, but a gun to use on certain occasions.
I 'd spend extra cash on the wood, and it'd make me smile every time I took it out.