I went the route of rebarreling a CZ527 in 7.62X39 for a Grendel. Worked out very well and is about all I hunt with these days. That could easily be done or a Howa Mini to 6mmARC., There are also some mini-mauser in 7.62X39, do not know of any that have done it but the Ruger Ranch is another.
Buzz you can find out some opinions from some that have done that over on
https://6mmarc.com.Any of the PPC bolt faces will work. If you want a Remington 700 in it you can get a bolt from Pacific tool and gauge.
With a standard short action you could throat it so those long pills can be seated out further.
Does this mean you are not switching to shotguns.