Hello, I just purchased a case of 50 rounds of what I was told was 45/70 at an auction. Trying to identify round, made from 45/70 brass .403 projectile (.40 cal?) Over all length loaded 2.88" over all case length 2.14". Rim has not been turned down although it does have a notch ground into it for what I assume was clocking the round to the chamber.
Looks like a .40-65 Winchester loaded for a single shot rifle.
That notch was to provide a reference mark so that a reloaded case could always be oriented the same way when placed in the chamber of the reloader’s rifle. It enabled the shooter & owner of a specific single shot rifle to reload cases with a minimum of effort; de-capping, cleaning the case and re-priming. The practice continues to this day, done here on a modern case. The bullet is a modern design intended only for single shot rifles. The .40-65 was originally marketed for repeating rifles.