Ben, what the double was is a Westley Richards hammerless double with what looks like 28" barrels, and is most likely a black, or Nitro for black double probably in one of the older .450 bore cartridges. I'm speaking of the rifle used in the movie. The Rimington character is fictional, and never existed. Addtionally i don't think there is mention of a double rifle at all in the book account of this happening. Col Patterson, and most others in those days used the 303 Brit bolt rifles. However, black powder rifles were used far later that 1898 in Africa, and India. I have a rifle that looks exactly tlike the one in that movie, that is chambered for 500/450#1 Express,made in 1892, and this is a black powder rifle made for deer hunting in those days. Many lion were killed with deer rifles in those days, as well as many hunters were also killed by lions, that weren't stopped by the small rifles, as the 450s were considered to be in the late 1800s!