During these plague times, the Royal Armouries has started up a few video series on YouTube, including one with Jonathan Ferguson, the Master of Firearms and Artillery. Back in March, he
took a look at a Treeby Chain Rifle, a .50 caliber rifle that used a chain of 14 chambers revolving around sprockets instead of a conventional revolver cylinder. It didn't have quite enough information to go on, but way back in the 1950s one had been test-fired for its centennial and written about in
Guns magazine. This had enough information to put together a rough set of statistics for the gun.
The most interesting feature is that it seals the gap between chamber and barrel by moving the barrel using a threaded sleeve controlled by a handle. This means the firing procedure is slightly more complex than usual. The lever is rotated so the barrel moves forward. Cocking the hammer then rotates a chamber into battery. The lever is then rotated back so the barrel slides over the tapered front of the chamber, and the gun can be fired. This added complication is likely why it was never ordered by the military, despite the weapon apparently working flawlessly in trials. Reloading is slightly slow because it uses loose powder and a ball inserted from the front and a cap placed on the back of the chamber, similar to an Agar (Coffee Mill) machine gun or the earliest Gatlings. Tests were done with a 30-chamber Treeby that apparently also worked well. It was able to fire all 30 shots in a minute, so the seemingly awkward barrel action didn't slow it significantly, albeit with a practiced shooter. In Tommy's hands, it likely would have had significant issues with firing without sealing.
Treeby Chain Rifle (12.7x44.5mm BP Ball)
Wt 4.8 kg, ROF SAR, Rld 2 per chamber, Mag 14, Dam 2, Pen Nil, Bulk 7, SS 1, Rng 75