Ephraim Sprague writes ...

I was sitting in the smoking room of Claridges enjoying a very nice port wine when I was aware of an older gentleman of millitary bearing being introduced to me by the porter. "Ah, young Doctor Sprague, over from the colonies I hear!" I smiled and replied, "No taxation without representation!!" which seemed to serve as a good icebreaker.
And so I met Colonel James Fellows, late of the 13th Bengal Lancers and veteran of campaigns in Sudan and Afganistan, a remarkable old soldier. The conversation turned to firearms and current trends in service sidearms when he told me of an unusual pistol that many officers purchased as personal weapons for campaigns in the late 19th and early 20th century. Reluctant to startle senior members of the club, he invited me round to his town house to view this fasinating pistol.

"A lot of the old boys had been through the Indian Mutiny and the talk of the officers mess was always how those little beggers would take a few pistol rounds and still keep on coming, so when I got posted to the Sudan I wanted somethng that was stop one of those Fuzzy-Wuzzies in their tracks. Off I go to the Army and Navy Stores 'cause in those days an officer had a lot of leeway in their choice of personal weapons and fell in love with this beauty as soon as I saw her. Fellow behind the counter said they were selling like hot cakes, popular with tiger hunters out in India by all accounts. The level of workmanship is quite evident in the checkering of the butt and the blueing as would be expected from the firm of Lancaster, who by appointment to His Majesty the Prince Consort supplied shotguns to the royal family. The locking mechanism is also shotgun-like as you can see, and operates a self-extractor. Feel the weight, hmm? 2 ¼ lbs so you run out of bullets, HIT THE BUGGERS! Now check the barrel bore and you will see it has an oval cross-section that twists down the barrel, imparting spin to the soft lead bullet giving it stability in flight. My batman Bates appreciated that because the barrel fouled less and was easier to clean."
"Now any layman with familliarity with multi-barrel weapons could be mistaken that the barrels actually revolve? Quite obviously the firing pin, moving along a sleeve, is rotated 90 degrees with every pull on the trigger. With no external hammer this means the trigger pull is quite heavy, not a problem with close combat work, but for shooting at distance I purchased one with a cocking trigger. Has a kick to her, but don't use those new smokeless powder cartridges or she will break your arm!"
"There you have it. Irony is I never shot anyone with it, but I did put a few rounds into something for all the good it did. But that is another story. Another brandy Ephraim?"

Game notes for Call of Cuthulhu®

Notes
Without the cocking trigger you would have to use the unaimed fire rule (CoC Ed 5.5 p.56) which lower the effectiveness of the Lancaster, but you would have two shots/round:-).
Ammunition is service issue but rare after the Great War.
Lancaster also made a two-barrel version and used the same firing mechanism on a four-barrel shotgun, but it was not popular due to barrel weight, but could make an interesting sawn-off.

Sources
Myatt,Fredrick (1989), "Pistols and Revolvers", London, Tiger Books Ltd
ISBN 1 85501 029 1 Out of Print