Evolution of the Rimfire Cartridge
The 22 rimfire cartridge is the most popular ammunition product ever conceived. Nearly every one of us started with a ”22” and still use rimfire rifles and handguns regularly in spite of owning more powerful firearms. Experts estimate that the world-wide consumption of 22 rimfire cartridges is in the billions of rounds per year! Yet today's 22 rimfire is the lone survivor of a much broader line of cartridges. 150 years ago, rimfire was the latest advancement in firearms technology. Having bullet, priming system, and propellant in a single unit (known as a fixed cartridge) was a tremendous leap compared to muzzle-loading separate components.
When firearms made the transition from muzzle-loading to fixed cartridges, the first successful fixed cartridge was a rimfire. "Rimfire" means that the priming mix was held inside the cartridge case in a hollow rim. This placement allowed the percussion-sensitive priming compound to be sealed from effects of weather, yet would activate when the hollow rim was pinched between the firing pin and the edge of the chamber.
The concept of the rimfire cartridge was proposed in the 1830's, but its commercial use did not begin until 1845. Flobert (”flow-BEAR”) developed small-caliber, breech-loading target rifles and the cartridges for them. The cartridge case was little more than a percussion cap with a flange or rim containing primer mix. A round lead ball was seated in the case mouth and lightly crimped to hold it in place. The primer compound alone provided sufficient velocity for short-range shooting; no propellant was used in the early versions. Flobert rifles were made in calibers as small as 4mm (roughly 16 caliber). 22 caliber BB caps made in Europe today are practically identical to Flobert's original design.
In 1857, Americans Horace Smith and Daniel Wesson improved on the Flobert concept, using a 22 caliber conical bullet weighing 29 grains. To provide enough energy to move the heavier projectile, they lengthened the case to accommodate a charge of black powder. Their new cartridge is today called the 22 Short. Smith & Wesson's revolvers designed to fire the new cartridge were an immediate financial success and permanently added Smith & Wesson to the roster of famous names in the shooting sports.
The rimfire system quickly expanded into new cartridges, and just about every imaginable bore diameter soon had a rimfire cartridge. Smith & Wesson made 32 RF revolvers that were quite popular with Civil War officers. The 32 revolver, although less powerful than the more common 36 and 44 caliber cap-and-ball revolvers, was accurate and could be reloaded very quickly when things went bad around you.
New 22's appeared, too. The 22 Long was a 22 Short case lengthened to hold more powder. The 29 grain bullet was retained, but the additional propellant meant higher velocity. Later, a 40 grain bullet was used in the Long case to provide better downrange performance when fired from a rifle. They called it the 22 Long Rifle-heard of that one?
Even heavy-caliber cartridges used the rimfire system. The US Military needed a way to convert its 58 caliber M1863 Springfield percussion rifles from muzzle-loaders to fire fixed cartridge arms. Erskine Allin, Springfield Armory's head armorer, developed a system in 1865 to cut away the top half of the barrel and replace it with a hinged breech block that screwed to the original 58 caliber barrel. A large 58 caliber rimfire cartridge was developed to fit the original bore but allow breech loading. Allin later refined his design for newly manufactured rifles using centerfire cartridges-it became the famous 1873 ”Trapdoor” Springfield.
Another successful series of big rimfire cartridge was developed for the Spencer repeating rifles used during the Civil War. The 44 Henry Flat rimfire was the cartridge that started Winchester's supremacy in the lever action market.
Limitations
A large rimfire case could hold respectable amounts of propellant. However, the hollow rim still had to be thin enough to permit reliable ignition, thus limiting how strong the case could be constructed. Another factor was metallurgy. In the 19th Century, metallurgy was still a developing science. The case hardens as it is formed, and must be annealed or stress-relieved to be flexible and strong. Failure of this post-processing step could leave the case brittle. A brittle case could rupture at the rim folds on firing. As more cartridge power was required, priming systems had to be developed that permitted thicker and stronger case. The modern centerfire cartridge was born, and changed.
The massive number of rimfire calibers existing in 1880 began to shrink, starting with the larger ones. The last surviving rimfire cartridges larger than 22 caliber, the 25 Stevens, the 32 Long, and the 41 Short, fell off US ammo lists decades ago. They have been subsequently loaded in foreign countries on special order, but are basically a dead issue. Special order ammo is to keep old guns shooting, not to service the needs of newly-manufactured firearms. As the old guns still being shot become more collectible and move from the range to collections, the need for special order ammo will probably disappear.
) and the rimfire is definitely .50" or very slightly larger.Centerfire case length is 2 1/8th in., and OAL is 2.5" or possibly 2 9/19 in.Rimfire case length is 1 3/4th in, with OAL of 2 3/16 or 2 3/4 in.