AussieGunWriter,
Beartooth bullets have a 525gr bullet designed especially for the Marlin 45-70. It will feed and extract as it is intended.
You are very much spot on about the Marlin Guide gun not being anything like a dangerous game gun. While not a stunt to hunt brown bear with one, it's almost unheard of for an actual guide to carry one. Simply put, to many parts in the old design, to many things could go wrong. They can lock up! A DG gun is a bolt gun in .375 and up.
