Is there a guide to ammo calibers that lay people can read and understand?

I was shown a pretty sweet .380 pistol (Kahr) and wanted more info on the caliber since the bullets looked really small. I Googled " Is .380 the same as 38 special" or something similar, and got the following:

This is craziness. At least metric and Empirical seem scalable.

Do I have to be a gunsmith to have even a rudimentary level of knowledge in gun caliber, chambering and load types?

There are too many informationers online to count. Knowing the actual diameter of a bullet (English and metric) is part of the fun of shooting. After that, you can graduate to the history of the cartridge’s development. And then move on to the amount of headspace and free bore on a barrel, rifling rate of twist, muzzle velocities for various slugs and amount/type of powder.

There are thousands of calibers, many of which are impossible to actually buy because they are either obsolete or homemade. Don’t sweat it, you just learn from experience but no, the names don’t have to make sense.

The second part of the number may also refer to something else, e.g. year of adoption (.30-06 is 0.3" and introduced in 1906), or the original powder load (.30-30 is 0.3" I think, and was originally loaded with 30 grains of powder). Or .357 is so named because SIG intended it to be a semi-auto with similar capabilities as revolver round .357 Magnum.

Identical .30 caliber bullets are used by a number of calibers, including .30-06, .308, etc. Confusingly, .30-03 uses different bullets because they are round nosed.

If you are asking how to compare two calibers, it can be done by a number of metrics, including velocity when shot through the same length barrel, bullet weight in grains, or “stopping power.”

Kahrs are considered to be extremely finicky, as in they need a “break in” period. Plus they’re owned by the Moonies, YMMV.

Then there’s the branded cartridges. You have bullets for automatic pistols with “nominal” diameters of .25, .32, .38, and .45 of an inch. They are surnamed “ACP” which stands for “automatic Colt pistol.” For decades I though ‘C’ stood for ‘centerfire.’ Still but none of them have a diameter exactly the same as the nomenclature.

Aaaand you have the commercial names. The 7.62mm NATO round is sold commercially in the US as the .308 Winchester, while the 5.56mm NATO is commercially known as the .223 Remington. Don’t bother with conversions. Those English measurements are purely commercial. Further, the .308 Winchester is really just a 30-06 casing cut down by 0.5 inches in length. The .223 Remington is a .222 Remington casing with the neck shortened for better feeding and ejection into and out of an automatic rifle.

Ok. “Stopping power” was my whole reason for even looking up the caliber. I’d appreciate any input on that.

The break in period I’ve heard of. I miss my Ruger p95, I should not have sold that. Break in is fine if it’s warranted in the long run.

The Kahr P380 and the other model, is it CW?, have been popular enough to have run out of stock in some places unless I’m misinformed.

If the Moonies own Kahr that’s news to me. Who cares if they get a few of my bucks anyways? They’re so far below ISIS, Scientologists and Fundies to even be on my radar.

Because of metric vs imperial vs customary units these things are confusing at times.

But specifically, the .380 is a 9mm bullet in a shorter brass with less powder. It’s not the same as a .38, it’s more like a .35.

I’ll tell you this, don’t underestimate the .380. In little plastic pistols like a Kel-Tec it kicks pretty good and really isn’t that much fun to shoot. It’s stopping power is adequate but that’s it.

They’re not identical, but close enough. These days, it’s pretty hard to buy a rifle in .223 or in 7.62x51mm, but they can shoot the nearly identical round. There is tons of talk online about whether it’s UL or not, but the general consensus is 5.56 rifle can shoot either, .223 only .223.

Wikipedia says that .308 is from .300 Savage; I don’t know the history of it to say if that’s true. Certainly, .308 was the replacement for .30-06: similar power in a smaller package.

Again it can be difficult to sort out the internet gun forum know-it-alls. Some will tell you that .380 is puny and you shouldn’t carry anything smaller than .40. IMHO whatever works best for you and if a larger one is too bulky/too few rounds/unocontrollable, then stick with this. I wouldn’t go much smaller though.

Didn’t mean to turn you off. It is owned by Rev. Moons son, and there are no shortage of borderline-fundie owned companies.

To add to confusion, there are 3 9mm rounds which differ by 1mm in length:
9x19mm aka 9mm Luger
9x18mm aka 9mm Makarov (the USSR’s answer)
9x17mm aka .380

…yet the 9x18 is actually bigger in diameter than the other two, and requires different bullets. In terms of power, they’re by length order, however.

Isn’t the Ruger version basically a Kel-Tec clone?

The thing about the .380 is its small form factor, 9mm and above get too bulky to be a CCW. A .380 to an unarmored chest will “stop” most people. If you need multiple mags or a .40, you’re at war, and should just run.

Shotgun for home defense, small but effective CCW for non-SWAT situations
magnified red dot, long mag, suppressed, AR15 with fully loaded rails for “squirrel hunting”. LOL

Don’t do it. Or rather, I implore you to shoot the pistol in question before you buy it. If, you get a reliable one, it’s great: very accurate, tiny, low recoiling for the size. But a lot of them aren’t reliable, even after the 200 round break-in period, replacing recoil springs, extractor and ejectors, and I’m not sure what to try next.

I think they’ve clued you in as to what makes .380 ACP (9mm x 17) different than 9mm Luger or Parabellum (9mm x 19). Neither one, and in fact no handgun cartridge that isn’t really a rifle cartridge (see the various giant revolver cartridges like .460 S&W Magnum), is a cartridge where “stopping power” is a concept that applies. That said, 9mm Luger will, with the right ammo, penetrate 12 to 18 inches into tissue while expanding, usually to .5-.6 inch in diameter. .380 usually won’t.

As I read further, I again want to emphasize that handguns will not usually immediately stop an assailant. Even if you shoot them in the chest. Even if you do it multiple times. Even if it’s a .44 Magnum, never mind a .40 S&W. I like this video, from a surgeon’s M&M continuing education conference, but there are others, claiming that 5 out of 6—it may be up to 6 out of 7—people shot with handguns live. As well as pointing out what I’ve written above.

As he states, the usual thing that happens when an assailant gets shot is that, if you’re lucky, he runs off. IF you’re not, he keeps fighting until either he suffers central nervous system problems or he exsanguinates enough to drop his blood pressure to where he loses consciousness. This can take awhile. Especially from your point of view if he’s still armed. There usually won’t be visible holes in the assailant at first. You may not even see blood at first, depending on the size of the wounds and where they are.

All I’m trying to say is that handguns, while an effective tool for personal defense, aren’t a death ray or a phaser from Star Trek, and your previous posts made me think that you might be under the impression that they were.

Great post by Gray Ghost, I agree with it entirely.

The thing about little tiny .380 pocket pistols is that they are generally very tiny and light so that even with the .380 round (compared to 9mm) they jump around quite a bit during recoil. Another thing with them is that many (not all) of them are double action only which means a long, heavy trigger press with a long reset (the trigger release before you can fire a follow-up round). This can be difficult to deal with for new shooters or folks with less hand strength.

Many smaller 9mm pistols are somewhat larger in size, but still sufficiently small to pocket carry or easily carry in a good (not a cheap) inside the waistband (IWB) holster.

Further, 9mm is significantly cheaper and more plentiful (even though less materials go into the .380) than .380. In short, I highly recommend understanding that a .380 pocket pistol may not be everything some would make it out to be.

Myself, I conceal a full-size gun most of the time. Concealing a gun really isn’t difficult if you get a good holster/belt combination so the smaller end of the 9mm spectrum is, in my opinion, the way to go for most people.

That said, the .380 is considered by many to be sufficient for carry purposes and the double-action only trigger is a very safe choice.

Either way I highly recommend getting some actual training and if possible, renting a few guns you’re interested in so you can shoot them and see what you do and don’t like about them. Many places can supply both in the right location.

Getting back to the original question, a reloading manual is a pretty good reference for determining differences between different calibers. Besides powder charges it will also show the bullet and case properties.

Since cartridge brass is easy to form, machinists and gunsmiths can start with a standard commercial brass case and modify it (and the gun chamber) to develop a new cartridge. This is called a wildcat cartridge. Some of these wildcat cartridges work so well that they are eventually standardized by the industry and become a commercially available cartridge. Even so, some are successful in the market and others not so much.

I often carry a Sig P938 in a pocket holster. A little thicker than the Ruger LCP or Keltek but the overall size is not bad. It’s a 9mm.

Maybe I can give you a condensed lesson involving commonly encountered cartridges.
In handguns:
.25 acp, .32 acp, .380 acp are all cartridges originally developed for use in smallish automatic pistols. None are particularly powerful. In modern loadings, the .32 and .380 are adequate close range self-defense loads if you can place your shots and remember you can shoot more than once. 9mm Makarov is equivalent in performance to the .380 and was developed as a combloc service round.

9mm, .40 S&W, .357 SIG, and .45 acp are all cartridges originally designed to be fired from full-size automatic pistols like police or military might carry. They are all decent performers for self-defense and arguments about which is “best” are to be avoided at all costs.

.38 special, .357 magnum, .44 magnum, and .45 Colt (sometimes called Long Colt) are all cartridges originally designed to be fired from revolvers. Only the .38 special is comfortable to fire from lightweight self-defense style revolvers. It was the standard cartridge used by police in the US for a very long time and is still a respectable performer. .357 magnum is a longer, more powerful version of the .38 special. It was also a popular cartridge among LE agencies. .44 magnum is a very powerful cartridge useful for hunting. .45 Colt, depending on the loading you purchase can be a powderpuff (Cowboy Action Shooting loads) or the equal of the .44 magnum (Buffalo Bore hunting loads).

These are the pistol loads most commonly encountered in the US at your typical gun store. There are many more out there. Most are obsolete or niche purpose.

If you want to know about rifle cartridges, that will take longer.

No. While similar the ruger is better made. I own a successful gun dealership and I no longer recommend Kel-Tecs. Too many had trigger problems. YMMV.

Oh nonsense. I carry full sized most of the time concealed. A paddle holster with a coat or suit/sport jacket covers nicely and a good holster prevents any sagging.

Yeah, they call them DAO, except technically they aren’t. The trigger doesn’t do all the work. Many of them need the slide cycled before they can be fired. So even while the hammer doesn’t look cocked, it is in a slight pre-cocked condition. What this means is there is no “second strike” capability if you have a misfire. If you don’t believe me take an unloaded Kel-Tec P3AT or Taurus 738 and dry fire it once.
click. Now without cycling the slide pull the trigger again. nothing. A True double action trigger cocks the hammer and fires the weapon with no motion of the slide needed.

That’s a single action pistol. How do you carry it? Condition 1, 2, or 3?

I was looking for some information on 38-55 for a 1894 winchester and stumbled upon this wikipedia page which may be of use for you.

It gives a few comments off to the side about interchanging ammo, obsolete, etc

I’m not under such a delusion. I’ve never shot a person, but I have used “mace” on a guy and it only made him madder instead of the face-clutching weeping you see on TV. I would never expect someone to be blown off their feet or drop like a stone no matter how many shots landed.

That was about as good an answer as I could have hoped for. Thank you.

Perfect! Awesome find.

Hijack: what information on .38-55 are you looking for, or did you find anything? My friend acquired one (forget what, but not Win 94) and is looking for ammo/reloading info; as it’s pretty obsolete it’s IIRC about $2/round.

Condition one always. In a DeSantis pocket holster. Sometimes in a belt holster but not often, depends on what I’m wearing.