If it is a 40/50 Straight should be no problem. If the bottleneck cartridge you need to check the shoulder diameter to the same dimension from the base on a 40/65 case to see if it will clean up.

Deadeye & jhm I appreciate the reply’s.  The seller is not sure which of the cartridges it is chambered for.  Barrel is marked 40 - 1 ¾ which seems to be a 1/16” off what   I might expect either the SBN or the straight cartridge to be?  I was hoping the BN would clean up to 40-65 win if that proved to be the chambering. It will on paper with no margin for error at the step to the neck. Jhm, I am guessing that was what you found.

The humor of it all is that I’d felt too old to get in line and wait a couple a years for a new Shiloh build and now at least a couple of years later I am still waiting on the used market to flop my gun, lately willing to get creative…..smile.

Chase...

This area is where I had the problem. Wound up having to set the barrel back to get everything to clean up which meant a lot of extra work.


JMH

Chase wrote on Aug 26^th, 2022 at 10:41am:


I think the .40 caliber old cartridges are all viable options, and I probably have more single shots in .40 caliber than any other bore size. 
I've never owned a .40-50SS as I've avoided that cartridge because of the brass and dies needed to shoot one. It can be tough to find, and expensive, so never interested me. The .40-50SS on the other hand uses cheap and plentiful .30-40 Krag or .303 British brass, so it's very inexpensive.
I have several .40-65 rifles, but my favorite is the .40-85/90 Ballard cartridge. It is a very versatile and accurate cartridge that works well with anything from a 350 gr. to a 410 gr. bullet in my rifles.