"...multi-barreled flintlock carbine, or whatever it was...it was impressive, but what a drag to reload in a fight!"
The Nock volley gun. If you read Bernard Cornwell's Rifleman Sharpe, his sergeant uses one.
I remember The Last Outlaw. I also remember what the Company Sergeant Major taught us during my recruit training. Always have toilet paper, and always count your rounds. both on loading and on firing.