>>64203298
Sounds like you'd really have to go custom if you want a 40/10mm; I don't even know if barrels are available for SMLEs in that caliber but I can't say I've looked. There are some DP rifles floating around out there and there is a 45 barrel available but it might not be full length, which bugs me. If the DPs last at the prices they've been (~$125-150) I might just grab one to see what I can do with it. 45 seems to play with the bolt nicely as-is but I'm not sure about smaller cases. IMO, 9mm would be nice as 45ACP is 31.6cpr before shipping on Ammoseek for a brand I actually recognize (that isn't steelcase/amount restricted). Blazer Brass 9mm is 19.4cpr w/o amt restriction. Only like 12cpr difference, but every 8.something rounds that's an entire dollar more. At least that's what I'd want if I did a pistol cal conversion and silenced it.
https://www.youtube.com/watch?v=hyq2UZk9Rv8
https://www.youtube.com/watch?v=4whGqT4y5Dw