I can make an argument that the big year in cartridge firearms was 1873 – the new guns were just improvements of existing designs, but all of those improvements included a single development – the centerfire primer.
In 1873, the new guns were the model 73 Winchester, the 1873 Trapdoor Springfield, and the 1873 Colt Single Action Army. Each was developed from a rimfire predecessor.
Let’s look at Colt first – the Army wanted more power than Smith and Wesson was offering, and Colt first offered up the 1872 Colt – basically the old percussion Colt with a new cylinder chambered for the 44 Henry rimfire . . . and the Cavalry officers remembered that the Dragoon Colt, a quarter century earlier, fired loads with 40 grains of black powder. They wanted that power back. In 1873, they got it – a cartridge that held 40 grains of powder, the Single Action Army was built with a top strap, and, while it may not have been in continuous production by Colt, someone, somewhere, has been building Single Action Army revolvers over the last 150 years.
That same 44 Henry rimfire brought in the Henry lever action – 16 shots fast back in the Civil War times. Oliver Winchester bought up New Haven Arms Company, hired Benjamin Tyler Henry, and began working on improving the lever action rifle – first with the 1866 Winchester continuing to use the rimfire cartridges, followed by the model 1873, with the centerfire 44-40. The old rimfire’s reliability had been enhanced by two firing pins (which made it easy to calculate the number of Henry rifles used at the Little Bighorn), and the similarity between the 45 Colt and the 44-40 Winchester led to an immediate development of the 1873 Frontier Colt – identical to the SAA except the caliber.
The model 1873 is produced at Winchester and available. Other copies, without the Winchester name have been available, though often made in Brazil or Italy. The 1873 is often called “the rifle that won the west.”
The third cartridge was the 45-70 Government – introduced along with the 1873 Trapdoor Springfield. Erskine Allin first developed the Trapdoor action in 1865, as a way to make use of the millions of muzzle loading rifled muskets left at the end of the war between the states – and those first trapdoor Springfields were chambered in .58 rimfire. I have no idea how many were made – obviously, the .58 rimfire wasn’t a particularly satisfactory cartridge – but ammunition catalogs from 1910 still listed the .58 rimfire.
The 1873 Springfield was used by the second-place finishers at the Little Bighorn on June 25 & 26, 1876, along with the Single Action Army Colt revolvers.
Production of the 1873 Springfield continued until 1893, in 1892 the trapdoor rifle began to be replaced by the bolt action Krag-Jorgensen rifle. Since there were only 30,000 Krag-Jorgensen rifles available when the Spanish-American War began, the venerable old 1873 Trapdoors came back in service to arm volunteer units.
If it’s a Springfield model 1873, it qualifies as a pre-1898 antique and is exempt from the registration and sales requirements of the Gun Control Act of 1968 – though some folks might argue against that interpretation.