Contrary to one thread running on this site, the Civil War did end, and the country was broke. It was broke, but needed a new and improved service rifle. Starting in 1865 a guy named allin started building breech conversions for the model 1861 Springfield, using the trapdoor design. The first ones were .58 caliber, the original bore of the Springfield. It was a .58 cal rim fire. The next generation Allin conversion was a .50 cal, in a .50-90 round. To get fifty cal they reamed and sleeved the barrel. The third geneeration they built a .45 cal barrel and sleeved the stock to fit the smaller diameter barrel, the .45-70. They had tens of thousands of the old 1861 rifles lying about and saved a fortune in tooling.
When the acceptance trials started there were several repeating rifles competing, such as the Henry, the mod 1866 Lebel in 8mm, and some single shots. Two important parts of the test criteria made the Springfield a shoo-in. Three, really.
One: The average guy that would be using these rifles would be some plow boy, dummer 'n dirt, and responsibel for maintaining the weapon. A lot of the guns were too complicated for him.
Two: They had a gazillion dollars worth of parts already in the inventory, and on any of these other guns they would have have to tool up from scratch, cancelling the advantage of having all those parts.
Three: The one that makes a lie out of every cowboy movie you've ever seen, is that it had to penetrate eight inches of fir plank at three hundred yards.
On the carbine version, much lighter, they changed to fifty grains of powder cause with 70 grains of powder it would kick the dog crap out of you.
A throw back to a simpler time, I suppose, but I really like that rifle.
When I was a kid, in Ariz in the fifties, I had one I deer hunted with for several years. When you reached out and touched a deer with one of those 405 grain slugs, he tended to stay touched.
I know that gun would not serve today with its single shot, but does the alternative have to be these stupid looking guns they're building today and using that very overused tacticcal description, or assualt this or that. The only one I almost like is that 25mm, if it works.
If I were to go into combat I would like to have an M-14 with select fire and a thirty round magazine. I wouldn't mind a shotgun with two barrels, One rifled for Sabot rounds and an improved cylinder for buckshot. The modern infantryman is lucky I'm not the pres, I would eliminate that total dependency on all that high tech crap.
Anyway, what got all this started is that the 1873 Springfield had one thing in common with the M-16. Ammo problems due to fouling that got guys killed. In the case of the 1873 the cases would stick in the chamber and the extractor would pull the rims off and then it required a special tool to get the case out. It's hard to do that when guys are shooting at you.