Well, to start with a bit of whining, the original design was by an American, Henry O Peabody. His design was one of many turned down after the Civil War in favor of the Springfield Armory's conversion of the 1864 Musket. The Peabody action was then improved by a Swiss designer, Friedrich Martini, to become hammerless and self-cocking, and the British decided to use a polygonal rifling developed by Scotsman Alexander Henry, and somewhere in the process someone decided they didn't need to give Peabody anymore credit, even though Henry's rifling really was only a variation on Whitworth rifling. The name ought to be Peabody-Martini, and someday, after all the other injustices in the world are righted, surely something will be done about this.
There was good reason to replace the .577 Snider ( and , by the way, though Peabody didn't get name credit, it was nothing compared to the bad treatment given to Snider) . First was the cartridge. The Snider was a conversion of muzzle-loading Enfield rifles, and the cartridge it used was a short one that would hold about 70 grains of powder to push a short, wide .577 caliber bullet along at about 1200 feet per second. That's similar to what the muzzle-loading Enfield would do (though it was discovered the Snider was more accurate) and the trajectory was, like the Enfield, therefore rather steep and the range rather short. By 1871 it had been generally discovered that a smaller caliber bullet of the same weight with a similar amount of powder would have higher velocity, so a flatter trajectory and so longer range. For the British, the 577/450 was the result.
The rifle also had advantages over the Snider. The standard design for muzzle-loaders had been lock, barrel, trigger, trigger guard etc, assembled into a wooden stock. Right where most of the hardware was embedded, the lock mortise, there was less wood, and that was often a weak point. The Peabody-Martini had replaced that weak mid-section with a steel receiver, and by bolting a straight buttstock into the receiver, it was harder for the rifle to be broken in the middle. The action was quite rigid and strong.. It was also quite quick to disassemble and clean- a very important thing for a black powder weapon! The Snider, like most muzzleloaders, had a side-lock with an exposed hammer. That meant that loading required both opening the breech and manually cocking the hammer, Having an internal firing mechanism , and a lever to quickly open the breech, meant that the-Peabody-Martini could fire a good bit faster than the Snider.
Shortcomings? The biggest was not in the rifle itself but in the ammunition. Around the time the rifle was being adopted, Lewis Carroll had introduced the doddering character of the White Knight, who was constantly saying "it's an invention of mine, don't you see". There was a good bit of experimenting with how to make brass cartridge cases, generally, but without a lot of field trials the British adopted very much a White Knight-sort of design that had a drawn and stamped brass base but also a rolled foil & paper upper part. These were very fragile: it was possible to take a 450/577 case and mangle it in your hands. When the gun got dirty, the case got stuck, and more often as not, it broke apart as it was extracted. When an expedition was sent up the Nile to rescue Lord Gordon in Khartoum in 1884, the Mahdi's forces , armed with Remington Rolling Block rifles, easily could keep up a higher rate of fire than the British troops, Charles Beresford saying later that a continuous stream of disabled rifles were being handed back to the officers , who extracted the broken cases and handed them back. Eventually the whole cartridge case was drawn and stamped, and breakage became less of a problem.
But even as the Peabody-Martini was being issued, in 1871, multii-shot rifles , ones with magazines , were being designed and adopted. The Turks bought a number of Model 66 Winchester rifles and used them to great effect against the Russians ( who still had their own Snider musket conversion, the Krnka) , the Swiss then quickly took the Model 66 magazine and incorporated into their bolt-action Vetterli. By the later 1880's, it was obvious that single-shot rifles were obsolete. Bolt-action rifles also had been shown to be the strongest and most durable of the breech-loading systems. The British adopted the quick-loading Lee-Metford. By then the French had come up with a workable nitrocellulose propellant recipe, and the Lee-Metford was replaced by the stronger Lee-Enfield, which, in various models, would pretty much stay standard for the next 60 years..
The Peabody-Martini action, though, survived quite a long time on the civilian market. As I said, it was quite strong, simple, and easy to clean, and quite a number of target rifles, hunting rifles and shotguns have been made with it. ( Statement of personal bias- I have a venerable BSA .22 Martini target rifle that is still may favorite for peaceful plinking)
Dennis Lewis: Martini-Henry .450 Rifles and Carbines
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