Centerfire or Rimfire


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highfive
August 12, 2007, 08:42 PM
Maybe is a stupid question but I'm not the most knowledgeable person in handguns yet, lol

I just would like to know what's the difference between rimfire and centerfire, I really don't have an idea. and maybe what's better if any.

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Sistema1927
August 12, 2007, 08:45 PM
A centerfire weapon has a cartridge that has a separate primer mounted in the cartridge case. A rimfire has the priming compound spun into the rim of the cartridge. The .357 magnum, .45 ACP, and 9mm are examples of centerfire in handguns. The .22 Short, Long, and Long Rifle are rimfire. There were early rimfire cartridges in larger bore diameter, like a .44, but they did not prove to be as reliable as centerfire and went the way of the dodo.

Many (but not all) centerfire cartridges can be reloaded by adding a new primer, powder, and projectile. Rimfire cartridges are a one shot proposition.

Quoheleth
August 12, 2007, 08:49 PM
It has to do with how the cartridge is ignited in the firearm.

In modern ammunition (as opposed to blackpowder), cartridges are ignited by means of a primer.

Centerfire cartridges have a primer in the center of the base of the cartridge. If you look at a 9mm, .38 Special, .357 Mag, .45ACP, .30-06, or 20 gauge (just as examples), all will have a smaller, center circle. That's the primer. It is struck by the firing pin which ignites the primer, which in turn fires off the powder load, propelling the projectile down the barrel.

Rimfire cartridges have a priming compound that is internal - you can't see it from outside the case like the examples above. The primer will strike the rim of the cartridge where the compound is compressed inside the cartridge. The process continues as above.

Generally, the only "modern" rimfire anylonger is the .22 - short, long, long rifle and Magnum - and the .17 Rimfires.

There were some rimfires in the late 1800s, but as far as I know, most - if not all - are obsolete as far as modern loads go.

If you want to know, look at the base of the cartridge. If you see a small circle, it's centerfire. If it's flat, it's rimfire.

Q

highfive
August 12, 2007, 08:50 PM
So rimfire is only made know for small calibers? and centerfire is for the big guys?

Jim K
August 12, 2007, 08:59 PM
Rimfire cartridges were among the very first fixed cartridges, that is cartridges that contained the priming, powder and bullet in one metallic "package" that was not only convenient but nearly waterproof as well. The cartridge fired when the gun's hammer struck the rim, pinching it between the hammer and the breech face; that blow set off the priming that was contained in the rim.

But as more power was needed, it became evident that the rimfire was not up to the task due to an inherent contradiction. If the rim was weak enough to be pinched by the hammer (using any reasonable force), it would be too weak to contain the pressures of a larger powder charge or the even higher pressures of the new smokeless powder. In addition, a center-fire round allowed simpler gun manufacture, as there was no need to offset the firing pin.

In the early period in the 1860's and 1870's, drawing brass was in its infancy, so there were several inventions covering manufacture of center-fire cases without drawing brass. Some used built up cases; others used copper almost as thin as that employed in rim-fire ammunition, and were not much improvement. Finally, manufacturers learned how to "draw" brass, starting with a solid disc and passing it thorough a series of dies until it became the cartridge case as we know it today.

Where high pressures are not a factor, as in small-bore (.22 caliber) rifles, the rim-fire cartridge is still used. It is inexpensive to make and serves the purpose well.

Jim

Jim K
August 12, 2007, 09:10 PM
Hi, Quoheleth:

"If you want to know, look at the base of the cartridge. If you see a small circle, it's centerfire. If it's flat, it's rimfire."

Mostly true, but just for fun, here is a picture of two cartridges. Guess which is rimfire and which is center fire.

Well, both are centerfire; the one that looks like a rimfire is Benet primed, the other is Martin primed. Both are 50-70.

Jim

Quoheleth
August 13, 2007, 02:16 PM
Well, I'll be...ya got me there, Jim. I stand corrected, and I appreciate the insight.

Don't think I'll have to worry about mistaking that big 'un for my .22, tho!!!

Q

40SW
August 13, 2007, 02:47 PM
quote

"So rimfire is only made know for small calibers? and centerfire is for the big guys?"


Don't be confused into thinking that rimfire is somehow "weaker" or "lower" in stopping power or power in general than a centerfire. or "small calibers". The .17MACH2, .22magnum and the .17HMR are excellent for varmint control.(all three are rimfire).

Example:
A 22 Magnum (rimfire) is of course more potent than any .25ACP (centerfire).

highfive
August 13, 2007, 07:23 PM
got it, thanks a lot guys now I now a little more and I'll keep learning and a lot times with your help. Thanks again

Vern Humphrey
August 13, 2007, 07:40 PM
Let's clear up something -- rimfires are limited by the thin brass in the head (base) of the case. While the .17 HMR and .22 WMR are impressive, they can't match something like the .22 Hornet, which can operate at much higher pressures because of it's thicker brass head.

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