Centerfire Vs Rimfire For The Total Beginner
A bullet comes one of two ways: rimfire vs centerfire. Most of them these days are centerfire, though the few remaining rimfire rounds remain quite popular.
A rimfire round lacks a primer in the base of the cartridge, whereas a centerfire cartridge has that little button in the center – hence the name! – and thus does have a primer that’s struck by the striker or firing pin. That’s the basic difference.
However, what are the major differences? We’ll go ahead and get into that. Obviously, centerfire rounds are more common these days as that’s what most rounds for target shooting, carrying concealed and so on, but there are plenty of uses for rimfire rounds as well.
Rimfire Vs Centerfire: Reconnoitering The Rim…Fire
So, to explain the difference between rimfire vs centerfire ammunition, we must address the difference in the primer as that is where the two bullet designs differ.
The primer, for those unaware, is a tiny powder charge that, when ignited, lights the main powder charge. Primers are made with a volatile shock-sensitive compound (such as mercury fulminate) that ignites when struck by a hammer or firing pin. With the advent of cartridges, the primer was moved from outside the chamber into the ammunition itself.
In making ammunition, a wet drop of the primer compound is applied to the primer or the cartridge. Primer compound is stable when wet, but quickly dries as the round is assembled. Once dried, it becomes shock-sensitive but is stable enough to be put in boxes, transported and so on.
What’s the difference?
To make a rimfire round, the bullet maker applies a drop of the primer compound to the bottom of an empty cartridge case. Then, the case is mechanically spun, creating a layer of primer compound around the bottom rim of the case. There is a small (we’re talking the thickness of a piece of paper) space inside the rim that fills up with the primer powder. The rim is struck by the hammer or firing pin (hence “rimfire”) and the powder is crushed inside the rim and ignited.
A centerfire cartridge, however, has a primer cap pressfit into a cavity at the base of the cartridge, in the exact center. Therefore, centerfire. A centerfire cartridge puts the primer compound at the very rear of the primer. Spark from the primer enters the main chamber of the cartridge and ignites the main powder charge, discharging the round.
Centerfire rounds use one of two designs, namely a Berdan or a Boxer primer. The Boxer primer has a single narrow channel that the spark ignites propellant through. A Berdan primer has an anvil-shaped block in the middle of the primer – referred to as an “anvil” in the technical literature – with two very narrow channels on either side, which spark from the primer enters the cartridge through.
Centerfire Vs Rimfire Advantages
If weighing the relative technical merits of centerfire vs rimfire, the centerfire design is the most advantageous up to a certain point.
Centerfire ammunition is, in a sense, better firstly for ease of manufacture. The primer is pressed into a case, powder added, the bullet seated and the bullet crimped together. Very simple, all things considered, and the round is stable.
Centerfire rounds are also safe, as a primer strike is needed to discharge the bullet. Granted, great care must always be taken with ammunition as part of proper gun safety, but the relative stability of centerfire ammunition is a definite boon.
Rimfire ammunition, however, is somewhat less stable. The construction of rimfire rounds – with a smear of primer inside the bottom of the rim – can lead to more dud rounds within a given lot of ammunition. Since rimfire ammunition is also more difficult to make – both in terms of machinery and also safety protocols – there are fewer factories and technicians capable of producing it.
In periods of high demand, shortages of rimfire ammunition can and do occur.
With that said, there is an inherent advantage to rimfire ammunition, namely that it is much easier to make rimfire rounds of very small diameter vs centerfire rounds of very small diameter. As a result, the smallest of bullets – such as .17 HMR and the .22 rimfire family – are much easier to make as rimfire rounds rather than as centerfire rounds.
Not that .17 or .22 caliber bullets cannot be made with centerfire cases, of course. They can and indeed are, but they are almost universally rifle cartridges. Some are small rifle rounds, such as .223 Remington/5.56mm NATO, and some are larger rounds necked down for a tiny bullet such as .220 Swift and .22-250 Remington, which are a necked-down 6mm Lee Navy and .250-3000 Savage, respectively.
However, very small caliber bullets are more easily made with rimfire construction.
The three most popular rimfire cartridges are .17 HMR, .22 Long Rifle and .22 Winchester Magnum Rimfire, aka .22 WMR and/or .22 Magnum.
There are some others that remain in production, however, though in smaller numbers. Target shooters still use .22 Short albeit infrequently, there are a few lots made here and there of .22 Long (like .22 LR, but weaker and with a longer case) and varmint hunters have some other rimfire rounds to choose from such as .17 HM2 (an improved .17 HMR) the 5mm Remington Rimfire Magnum (still in limited production though no guns are made for it anymore) and a few others.
Of these, of course, .22 LR is the most popular.
In the early days of cartridge ammunition, rimfire rounds were far more common. The original Henry rifle used a .44 caliber rimfire round (.44 Henry) and rimfire rounds such as .46 rimfire, .38 rimfire and .31 rimfire were commonly used in black powder revolvers that had been converted to fire cartridges as percussion revolvers fell out of popularity.
However, by the late 1800s they had become less common. The story goes that production pretty much ceased on all rimfire rounds bigger than .22 LR around World War II and basically never resumed since there was no real reason to.
The first centerfire cartridges emerged much earlier than some might think, though they were mostly a curiosity until sufficient design improvements – along with the advent of repeating rifles – made it so there was pretty much no point using anything else.
Early centerfire ammunition (though without a primer) emerged before 1820, but the first centerfire ammunition featuring a primer were devised around 1830 by a French inventor, one Clement Pottet. Pottet’s first design was a paper case with a brass base. The shooter manually inserted a primer to be struck by a firing pin.
By 1855, Pottet’s design had evolved to a brass base with a primer countersunk into the base, with a paper case, which would be recognizable to the modern shooter. Brass cases soon emerged along with the Berdan and Boxer primer designs (both in 1866, with the former being devised shortly after the latter) and the modern centerfire cartridge was born. Smokeless powder entered the picture at the end of the 19th century.
Rimfire Vs Centerfire Ammunition
At this point, rimfire vs centerfire is a moot point in most practical terms. What rimfire rounds remain are mostly for plinking and target practice though are also good for varmint and small game hunting.
Centerfire cartridges have some inherent advantages over rimfire from a purely technical perspective.
First, the use of a primer cap instead of a primer compound at the base of the round makes them inherently more stable and safer to store and transport. Ignition is also more reliable. Though dud rounds do occur no matter what ammunition you use, it happens a bit more often with rimfire ammunition.
Secondly, the Boxer primer design makes for easy extraction of a spend primer case and insertion of a new primer. The case, therefore, is reusable and the crafty/thrifty shooter can reload cases as many times as the case allows for it. How many reloads depends on what round you’re loading and how you’re loading it. A lower-pressure round such as .38 Special can be reloaded many times but a .30-06 or .338 Winchester Magnum will require new brass after a few reloads.
Reloading rimfire ammunition, however, IS actually possible. There are reloading kits out there for .22 LR that allow the handy and crafty shooter to reload, though great care is required. It’s also a delicate procedure, requiring assiduity and finesse. It’s time-consuming as well, so you aren’t going to be making dozens of rounds in a sitting. That said, it is totally doable if you wanted to.
Fewer people handload these days, however, and the hassle of doing so relative to the inexpensive cost of .22 LR…may put some people off.
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