Try a factory round.Williams cartridge “factory reloads”
A 'Factory Reload' may not be properly resized.
You never know what their brass was fired in before they reload it. If the case hasn't been sized all the way
down to the rim to bring it back to a factory chamber spec, it could be too fat and hang up going in that last little distance.
If you suspect the 44-40 throat/neck is a bit on the small size, use a Factory 38-40 round to check just the base end of the chamber
The smaller dia bullet and neck will by-pass any 44-40 neck & throat and just give you a reading on wether the chamber base is accepting a factory cartridge or not.
Check that chamber mouth edge at the extractor cut as suggested already also.