In order to fully understand the answer to this excellent question, it's IMO necessary to know the history of firearms development spanning the immediate post-war (War Between The States, that is) period, and the turn of the following century. LOTS of important things happened during those years, and a lot of important developments in the firearms field happened too.
It was the War Between the States that was responsible for the burgeoning popularity of 1)self contained cartridges, and 2)repeating firearms designs using self contained cartridges. There was an absolute plethora of single shot cartridge firing rifles and carbines produced during the war years, by every inventor who hoped to grow rich off wartime contracts. Given that the technology was in its infancy, of course, most of those designs for cartridges and the firearms which used them were proprietary in nature. In other words, there was no standardized design for cartridges that could be used across the design field- so each rifle design used its own ammunition and could not fire that of another make. Military officials were hidebound traditionalists in those years, and slow to change. They resisted strongly the imposition of new technology for many decades, preferring the tried and true weapons of years gone by they had known when they were junior officers in the ranks.
This backwards-looking attitude lasted until the turn of the 20th Century and after, BTW- note that the vaunted 1903 Springfield rifle still had a magazine cutoff switch, so that it could be employed as a single loader with the magazine held in reserve. The point? Officers did not trust troops not to waste valuable ammunition, as they feared would happen if troops were allowed to employ their rifles as repeaters.
But the troops- ah, the troops seemed to understood the value of firepower long before the concept became a watchword in the officer corps. I and others have long held that 'technology dictates tactics.' Here's an example. Imagine yourself going into a fight with a muzzle loading long gun. Number one, you can't reload the thing lying down- you have to be standing up to pour powder down the barrel, shove in a projectile, ram the whole thing home. You need fire superiority to win engagements- the only way to obtain overwhelming firepower with frontloading long guns is to have troops standing in mass formations shoulder to shoulder, so as to cram the most possible single shot slow firing weapons into the smallest space on the battlefield. Is that something you'd like to be a part of? Well, me neither, thanks.
It took vast amounts of drill to discipline troops to stand for the kind of punishment large formations in close order took on those historic battlefields. In fact, the high stiff collars on some military uniforms of the time were designed to keep troops from being able to turn their heads, to prevent them from looking to either side and seeing the carnage among their comrades. Of course, there were always NCOs nearby with swords to 'close the ranks' and discourage turning and running... .
So, suppose some yesteryear defense contractor came along and offered you a weapon that is NOT a frontloader. You don't have to be standing up to load the thing under fire in the open field of battle, it loads at the breech, not the muzzle. And you don't have to load powder, ram home a projectile, then prime the thing in order to fire it- reloading is now one step, not three. Would you think this was a revolutionary development?
With the above as a given next step, suppose a year later the same contractor shows up with a magazine gun using self contained cartridges that allows you to reload the thing with a simple movement of one hand. How would you feel now? You can stay behind whatever cover there is, prone, kneeling or standing, and fire repeatedly AND QUICKLY until you have to recharge the magazine. Would you be overjoyed at this new development or what?
There was a time in history when being 'heavily armed' meant exactly that- you had to be carrying a separate firearm for every one or two shots you were going to fire rapidly. You were literally weighed down with iron if you needed to be prepared to shoot several times in rapid succession. I recall reading descriptions of early travellers in dangerous areas, carrying one or two long guns and several single shot pistols in order to be able to fight off attackers.
If you give this state of affairs some serious thought, you will understand what a comfort a Colt revolver or two could be among those who lived 'in harm's way.' And this was long before the era of the repeating long gun firing self contained cartridges- there were revolving cylinder long guns, to include shotguns, available at the time- but they took a LONG time to reload when empty.
So we progress, from frontloading single shots and repeaters, to breech loading single shots using self contained cartridges, to repeaters using self contained cartridges. Note that all this happens over a pretty short time period, relatively speaking- from the first Colt revolvers in the late 1830s to the black powder cartridge repeating rifles of the 1860s. Over the next 30 years a lot more changed as well. Priming systems standardized to centerfire for large bore rounds and became more reliable, cartridge cases became stronger, cartridge designs standardized, and new firearms designs were produced to use them.
Even so, the self contained cartridges of this era still used black powder, you will remember. If you've never used a black powder repeater, you are unfamiliar with the quantity and obstructiveness of the fouling that black powder produces when it is fired in a mechanical device. It was a problem in the early lever action shotguns manufactured by Winchester, and caused issues in Winchester's earliest slide action repeater, the Model 1893, as well. (
http://www.texasranger.org/dispatch/11/Pages/Winchester.htm )
Never heard of the Winchester Model 1893? Well, don't worry. But before we cover the history of this ancient cornshucker, let's talk about a couple of even earlier pumpgun designs.
First was the Spencer pump design of 1882. Though it looks a bit odd by modern standards, its design was essentially the same as today's slide action repeating shotguns. It was of conventional design- tubular magazine under the barrel, sliding forearm reciprocation on the magazine and actuating the bolt inside the receiver etc. The Spencer was designed and produced as a sporting gun- its utility as a fighting shotgun was mainly recognized by customers. See a picture at
http://www.armchairgunshow.com/images/SG-1099.jpg .
The first genuine fighting shotgun with a slide action design was the Burgess. (
http://shootingbums.org/hvr/burgess.html ) Initially produced as a sporting gun in the mid-1880s, the Burgess was actually faster firing than the Spencer it competed with for sales. The Burgess had a reciprocating slide on its stock, rather than on the magazine tube. Realizing its potential utility as a riot gun or guard gun, Burgess produced the gun with a 20" barrel. Seeking contract sales, he had the gun demonstrated for Theodore Roosevelt, then president of the New York City Police Board, in 1885. The gun folded neatly in half when taken down and could be packed in a holster under a coat out of sight, loaded with six rounds and ready to be snatched out of hiding, flipped closed and emptied in about as much time as it takes to tell it. Exhibition shooter Charlie Dammon strolled into TR's office one day with a disarming smile on his face and a Burgess Folding Shotgun under his coat. Dammon exchanged a few pleasantries with the future president if the US, then suddenly whipped out the shotgun, snapped it closed and blasted off six rounds of blanks. TR was so impressed at the demonstration he ordered over 100 of the guns for the New York State Penal System (they were sold at auction in Canada in about 1920). Famous lawman Pat Garrett owned one of these interesting pumpguns. Burgess used this style of pump because he lost a patent dispute with Sylvester Roper, who was Christopher Spencer's partner in the Spencer Arms Company referenced above (the patent was #255,894).
Winchester was quick to recognize the competition to its own repeating shotgun designs and bought out the company from an ill and retiring Burgess in 1899 after several years of negotiations. All the available Burgess guns were then withdrawn from the market and Winchester converted the machinery used to make them to its own uses.
Gonna take a break here, and return later for Part Two of the impromptu history lesson- if y'all want to hear it, that is.
lpl/nc