Ballistics Question: Why is rimfire rimfire?

[terryg]

Here is something else I have wondered for quite sometime:

Is there any specific advantage to rimfire over center fire? The Wikipedia article talks a bit about the history - but doesn't speak to performance. I know there are a few other calibers, but it seems that 22 is the primary rimfire round.

Is there a specific benefit for smaller calibers? Or has it hung around so long just because 22lr became popular? (Like VHS over betamax?) I seem to remember hearing/reading that rimfire cartridges can be (slightly?) more prone to squib firing and other primer mishaps.

Part of what drives this question is the presence of the rimfire only range at PSC. What's so special about rimfire? If there was a center fire 22 (or similar caliber round), why would you want to separate it from other similarly powered weapons? Why not call it a small caliber long gun range? Not that I am hung up on terminology - 'rimfire' is obviously shorter and easier to say. I am just wondering if there is more to it than that.

Thanks in advance,

t

[AEA]

I don't think there is anything special about it. It was a natural progression from cap & ball firearms to a cased cartridge. It came before centerfire.

Ever see a .41 rimfire derringer? Many other calibers were rimfire as well, including large caliber rifles.

The only reason I can see that the .22 is still rimfire is because there is not enough room for a primer.

Why a separate lane for .22? Probably to keep the brass separate from other (centerfire) brass.

[Middle Age Russ]

Rimfire simply refers to the mechanism which ignites the round. The reason you see .22 LR and magnum and the .17 rimfires is that they are cases which do not have a large enough, or strong enough base to take centerfire primers. Instead, they spin the priming material while it is wet into the rim. When the rim is suddenly compressed this priming material ignites, setting off the round.

Rimfires in common use today are typically low energy, small caliber cartridges, which is probably why they are segregated on the PSC range.

[A-R]

The only reason I can see that the .22 is still rimfire is because there is not enough room for a primer.

THIS

Rimfires in common use today are typically low energy, small caliber cartridges, which is probably why they are segregated on the PSC range.

AND THIS

[puma guy]

The restriction to rimfire at PSC has to do with limitations at that particular range I believe. Berm design and strength, etc. I recall that it's also restricted to .22 caliber RF and .17 cal RF is restricted. At least it was the last time I was there.
Rimfire cartridges were among the earliest development in cased cartridge design and had the priming compound around the rim were the firing pin could strike and crush it. Rimfire catridges were made in large caliber blackpowder chamberings also. For larger capacity blackpowder cartridges/shot shells (and later smokeless nitro cellulose powder) center fire was more conducive to consistent ignition and the rimfires were by design thinly constructed and not suited for higher pressures. The priming compound is in the cup and an anvil provides the surface against which to crush the compound and can be surrounded by a substantial cartridge head. I''m sure some one with more expertise that I possess can further elaborate. .22 caliber rimfires obviously would be hard to design with a primer and they maintain the original design conformation.
EDIT: I see some beat me to it.

[OldCannon]

Reloading rimfire is pretty much impossible to do without factory level tools (centrifuge, etc). Even at a factory level, reloading is too risky because of rim weakening. Lastly, for factory loads, it's easier to quality control centerfire vs rimfire loads.

Then there's the whole caliber issue -- small rimfires are easy to make in manufacturing, but large ones are VERY tricky. Too much primer in a large rim would result in rims being blown off, too little and you would have a hang fire.

EDIT: It's not like I'm some old timer that knows a lot of things about reloading (I'm more like a mid-timer ). You can easily find information like this in books like "The ABCs of Reloading" (highly recommended)

[Dave2]

Reloading rimfire is pretty much impossible to do without factory level tools (centrifuge, etc). Even at a factory level, reloading is too risky because of rim weakening. Lastly, for factory loads, it's easier to quality control centerfire vs rimfire loads.

I wonder how hard it is to melt and re-"forge" the cases?

[jimlongley]

OK, when Flobert developed the first rimfires, in the 1830s, he was among many searching for a solution to the thorny problems surrounding breech loading ammunition. Flobert's solution was to incorporate the priming compound in a little case: which could then be either inserted in a larger cartridge case, which is the way most "centerfire" ammo works today; or it could be used as an initiator separate from the case, as in semi-fixed or bag artillery ammo; or it could be even loaded with a projectile and shot as a complete fixed cartridge.

The last was the predecessor, in the 1840s, to the 'BB' Cap, or "Bulleted Breech Cap" which would be a "breech cap" with a bullet in it, a breech cap being the above mentioned semi-fixed or bag gun initiator.

This led to a whole raft of rimfire cartridges, the .22 series (Short, Long, Long Rifle, BB Cap, CB CAP) being the most ubiquitous, but even .62 caliber arms were made in rimfire (partly because the bullet molds existed for the muzzle loaders) and rimfire became, for a time, THE priming system of choice.

It was not unusual to hear tales of reloading rimfire, and I know of collectors who did so with their old rimfire guns, but it is a touchy thing, and you kind of need to be sure that the firing pin will strike a part of the rim that has primer in it instead of the part that has already been crushed.

It would not be economical to try to melt down rimfire brass and remake them, as placing the priming compound would be the same in a newly remanufactured cartridge as in a fired one. And the process to make a modern rimfire cartridge is very similar to what it was back then, a dime size billet of case material is physically formed into the cartridge case in a series of steps starting with forming a dimple, stretching the dimple to cartridge length, and then forming the rim.

There were many other competing priming systems developed in that period, including pinfire, teat fire, and needle fire, but rimfire had them all beat for simplicity and conveniently also worked well as a primer for bigger stuff.

Class dismissed.

[puma guy]

I knew someone with some expertise would come along. Thanks, Jim for the primer on primers! ( Yeah, I know - groans are forthcoming)

[terryg]

Again, I thank you all!

[OldCannon]

C'mon Jim -- finish the story -- you need to tell the part about the Boxer vs Berdan Primers war

[puma guy]

C'mon Jim -- finish the story -- you need to tell the part about the Boxer vs Berdan Primers war

[jimlongley]

More like Boxers and Briefs -

Berdan's primers depended on an anvil incorporated in the cartridge base to provide something to crush the primer against.

Boxer came up with a way to incorporate the primer in the primer itself, which made the act of reloading easier because a decapping tool could push the primer out of the primer pocket, an act that is essentially impossible with Berdan's system.

Berdan's primers resemble percussion caps, thus they are "briefer" than Boxers.

[OldCannon]

More like Boxers and Briefs -

Berdan's primers depended on an anvil incorporated in the cartridge base to provide something to crush the primer against.

Boxer came up with a way to incorporate the primer

oopsie...think you meant "anvil"

in the primer itself, which made the act of reloading easier because a decapping tool could push the primer out of the primer pocket, an act that is essentially impossible with Berdan's system.

Berdan's primers resemble percussion caps, thus they are "briefer" than Boxers.

Ah, very clever

[jimlongley]

Boxer came up with a way to incorporate the primer

oopsie...think you meant "anvil"

in the primer itself, which made the act of reloading easier because a decapping tool could push the primer out of the primer pocket, an act that is essentially impossible with Berdan's system.

Berdan's primers resemble percussion caps, thus they are "briefer" than Boxers.

Ah, very clever

Yeah, I meant anvil.