The 40-65 Winchester was introduced in 1887 for the Model 1886 Winchester rifle. The 40-65 was a further effort to put more steam in the repeating rifles� cartridges so they would be competitive with similar single-shot cartridges. Properly loaded it should perform well on deer sized animals. 

This text is based on information from “Cartridges of the World”, Hodgdon reloading manual, the cartridge designer and/or own resources.