RE: .450Marlin Bolt Action?
Hmmm....
I had a 45-70 in a big Siamese Mauser with a 26 inch barrel, sold it ..... to me it was little more than a curiosity; HOWEVER,
I believe Marlin makes a " cowboy" version in the 45-70 or 450 Marlin that has a longer barrel. Now you have the best of all worlds: strong cartridge, long enough barrel to capture its full power, a strong action (okay, its not a Mauser) and rapid fire capability. That' s the direction I would go provided I' m correct on the " cowboy" model.
Never Go Undergunned,
EKM