I’ve seen comments in some of the gun threads about centre-fire bullets being more powerful, and I notice that there is no limit on magazine size in Canada for rim-fire, while there are limits for centre-fire.
What is the difference between the two types of ammunition? Does it affect the type of firearm they can be used in? Is centre-fire a higher velocity? If so, why?
Looking for technical information only, please.
A rimfire cartridge has the primer spread in a small ring around the inside base of the cartridge. The firing pin strikes the edge of the cartridge which ignites the primer and thus the powder inside the casing.
A centerfire cartridge has the pimer in the center of the cartridge. Its pysically a seperate piece that must be inserted into the casing during manufacturing. This also makes most centerfire cartridges able to be reused.
Rimfire cartridges are generally smaller calibers because the casing must be thin enough to deform under the impact of the firing pin. .22 long rifle is perhaps the most common. There are .22 caliber centerfire cartridges (the .22 hornet) that are more powerful but they’ve been mostly supplanted by calibers like the 17HMR, which is a powerful rimfire cartridge – but still not as powerful as most centerfire calibers.
Here you go:
You’re going to get high pressures with centerfire rounds. Centerfire is also more reliable. Not that rimfire is unreliable but you do get more misfires with it.
Only .22 caliber firearms use rimfire cartridges. The .22 cal firearms / cartridges are the least powerful firearms / cartridges in use today. Every firearm not a .22 caliber, from a .17HMR varminter to an .456 elephant gun uses center fire cartridges.
The .22 cal rimfire cartridges have a simple and inexpensive, paper-thin brass casing that can be dented by the hammer of the gun, igniting the primer deposited in the rim of the cartridge. This neccessitates a low-power load.
Higher power center-fire cartridges need to have much stronger casings to withstand their powder loads, and so have a primer cap located in the center of the strong base of the cartridge, that is easily detonated by the pin, struck by the hammer of the gun.
As noted some .22 caliber cartridges such as the .22 Hornet are centerfire.
The .17HMR is rimfire, not centerfire.
Historically there have been larger rimfire calibers. Henry made a .44 rimfire lever gun in the 19th century, for instance.
Encased ammunition (like that used in all modern firearms) has two elements in the firing chain: the “primer”, which is a primary (impact sensitive) explosive which initiates the the combustion process; and the “powder” (actually often a flake or extruded shape), which fills the main part of the cartridge under the bullet (the projectile) and generates the pressure that propels the bullet down the barrel. There are two basic configurations for encased ammunition: rimfire, in which the primer is spread around the aft rim of the cartridge (which is shaped to form a grove) and the firing pin is a rectangular section that strikes the rim; and centerfire, in which the primer is contained in its own tiny case which is then fitted into a pocket in the aft of the case that has a hole leading into the powder.
Rimfire cartridges were common in the early days of encased ammunition because of the reality simplicity for manufacture but the only common rimfire ammunition available today are the .22 Long Rifle and .22 Winchester Magnum (yes, there are other .22 caliber cartridges and specialty rounds like the .17 Hornaldy Magnum Rimfire but these are not ‘commonly’ found in a large variety of firearms), both of which are used in pistols and rifles but not generally as service or standard defensive firearms. Most modern ammunition primarily intended for use in service handguns and personal defense weapons (PDW) is centerfire, including the .32 ACP (7.65 mm), .380 ACP (9x17 mm), 9mm Parabellum (9x19 mm), .40 S&W, 10 mm Auto, .45 ACP, FN 5.7 x 28 mm, HK 4.6 x 30 mm, as is all modern large bore rifle ammunition.
Rimfire ammunition has a reputation for being less reliable due to uneven spreading of the primer around the rim and the primer going bad because it is not hermetically sealed. Centerfire ammunition is much more reliable and can be easily loaded by hand with purchased components (primers, cases, powder) and either purchased bullets or those cast by the reloader. Almost nobody reloads rimfire cartridges (I’m sure there is someone out there who does but there is no real point).
The distinction mentioned in the o.p. is that the .22 LR and .22 WMR, while capable of doing significant damage and (in the case of the .22 LR) being commonly used in crime, is perceived as being less dangerous than large bore centerfire ammunition and primarily used by recreational shooters and small game hunters although the reality is that the .22 LR is quite a deadly cartridge albeit causing a lot of deaths by fragmenting and ricocheting around inside the body and producing infection that kills the patient. There is also a large aftermarket of really high capacity magazines in these chambering as well as handguns built to carry up to 30 rounds because of the small diameter and light weight of the cartridge. There are high capacity centerfire handguns (starting with the so-called ‘wondernines’ in the early ‘Eighties although the Browning Hi-Power was actually the first production double stack magazine pistol) and large capacity magazines intended for use in carbines and submachineguns, or just people who like having a large magazine awkwardly sticking out of the butt of their pistol to snag on everything for some reason.
Stranger
And of course .223 / 5.56x45.
A completely obsolete design is pinfire, which has a protruding pin get whacked.
Generally speaking, you shouldn’t dry fire a rimfire, while it’s okay with centerfire. There are exceptions: Ruger says it’s okay for their 10/22 and maybe others, while you generally should get cheap insurance for center fire dry firing in snap caps.
You can reload rimfire but it’s mostly a proof-of-concept. It’s not economical nor reliable. Centerfire has a replaceable primer as mentioned above, most US-produced ammunition uses Boxer primers so is reusable until the brass gives out, ammo produced by the Soviet Bloc and modern counterparts is often Berdan primed, so again can be reloaded but generally is not as it’s a hassle and not economical.
The reason that it is recommended to not dry fire a rimfire pistol regularly is because the firing pin will impact the breechface and eventually leave an indentation that can cause the spent cartridge to jam upon extraction. Of course, with many .22 pistols and rifles, dry-firing is the only way to drop the hammer on an empty chamber, and doing it once in a while is not a problem but you just shouldn’t make a habit of doing so frequently.
While that problem doesn’t exist with a centerfire (as the firing pin is centered on the axis of the bore) excessive dry-fire stresses the pin (because it is hardened steel that is intended to impact the soft copper of the primer) and will eventually result in fracture. If you want to practice dry-firing a pistol you should definitely use snap-caps, and many gunsmiths actually recommend storing an autoloading pistols with a snap-cap in the chamber so as to prevent damage from dry-firing and dropping the slide on an empty chamber.
Stranger
I own a set of snap caps for dry firing, I was warned that it was better for the gun.
This reminds me of a quote from Steve Martin’s character in the film My Blue Heaven.
“Richie loved to use 22s because the bullets are small and they don’t come out the other end like a 45, see, a 45 will blow a barn door out the back of your head and there’s a lot of dry cleaning involved, but a 22 will just rattle around like Pac-Man until you’re dead.”
What does it mean to dry fire?
When I took my kids to YMCA camps, they had .22 rifles for us to shoot as one of the activities. They were very light, not very loud, not much kickback. They seemed like one step above a powerful BB gun. Would those have been rimfire?
Yes.
.22 is (was?) cheap fun.
You unload the pistol, then pull the trigger. I was also told by someone not to do this.
I have seen those rim-fire .22 LR used as introductory target shooting for kids with a simple bolt-action rifle; I’m sure that is not uncommon.
Thanks!
Yes, once or twice shouldn’t be bad in either case, but snap caps are like $15 for a half dozen, cheap investment.
Additionally, .22 is a rimmed cartridge, which means the base is significantly wider than the rest of the brass. Most modern centerfire is rimless, semi-rimmed, or belted instead, except revolver rounds. What this means in this case is that in non-autoloading .22 LR rifles, you can also shoot cartridges which are the same dimensions except length, so .22 Long/.22 Short/.22 CB, .22 BB will work, and some are pretty damn quiet. But I’m guessing it’s just standard .22LR in this case, cheaper and easier to acquire.
Is that so that the cartridge doesn’t just fall out of the front of the cylinder?
Pretty much.
This can be key in the event of a Zombie Apocalypse, since I believe it is a law in the US that every pickup truck has to have an ancient box of .22LR in the glove box. (Just checked - mine is a box of Peters dating from Holy Crikey! 1944!)
Annnd we’ll avoid the ancient history of revolvers that use rimless rounds!
Sort of. Generally, rimmed cases are straight-walled and the ‘headspace’ (the measurement that controls the overall length of the round) off of the rim. This means that a revolver can be designed to shoot rounds of the same bullet diameter and case diameter but of different case lengths, which is why you can shoot .38 S&W Special in a revolver chambered for .357 Remington Magnum, and the same for .44 S&W Special in a .44 Remington Magnum revolver. Rounds designed for pistol shooting such as the 9mm Parabellum, .40 S&W, and .45 ACP are described as ‘rimless’ (actually having a rim that is just flush with the diameter of the body of the case and forms the extractor groove) or having a ‘rebated rim’, and are either straight-walled (.40 S&W, .45 ACP) or have a slightly tapered case (9mmP), and are headspaced off the rim. (There are also bottlenecked cartridges such as the .357 Sig and 7.63×25 mm Mauser which are headspaced off of the shoulder but I don’t know of any revolvers chambered for these so they don’t apply to this discussion.)
When shooting straight-walled or slightly tapered cartridges in a revolver one generally has to use what are called ‘moon clips’ or ‘half-moon clips’, which are just flat metal templates which hold the rounds by the extractor groove. This is more to allow for easy extraction, at least in the case of the 9mmP where the taper would hold the case inside the chamber but after firing they would basically be jammed in the cylinder without having the moon clip to extract them. Conversely, there are autoloading pistols designed to shoot rimmed revolver rounds but they generally have reliability problems because the protruding rim tends to complicate feeding.
In the case of a zombie apocalypse, you should eschew the .22 LR and own this gun, not because it is in any way reliable, accurate, or effective, but just to show off as the ultimate prepper right before dysentery takes out your entire group because you didn’t spend a few bucks on water treatment and filtration. It’s always the little details that kill you.
Stranger
You’ve been around guns and YouTube too long when you know what gun, and what video about that gun, that link went to without even hovering over it.
I love some of the comments:
honor harrington
[2 years ago]
That gun would drive Forensics crazy. “How many shooters?” “One or two to six.” “What!?” … “What about ID’ing the guns?” “No or partial Rifling.”