# Please explain bullet sizes for guns (and other ammo jargon) **URL:** \ **Category:** Factual Questions\ **Created:** [June 10, 2022, 10:49am UTC](https://boards.straightdope.com/t/please-explain-bullet-sizes-for-guns-and-other-ammo-jargon/965964 "2022-06-10T10:49:23Z")\ **Posts on this page:** 20\ **Page:** 3
**Author:** ![running\_coach](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/running_coach/32/15836_2.png) [@running\_coach](https://boards.straightdope.com/u/running_coach)\ **Post date:** [June 12, 2022, 8:39am UTC](https://boards.straightdope.com/t/please-explain-bullet-sizes-for-guns-and-other-ammo-jargon/965964/41 "2022-06-12T08:39:47Z")
> [@Whack-a-Mole](#): > > #1 in your picture is “caseless” but it sure looks like there is a case (albeit different from the other bullets). > > What does “caseless” mean? - To go with @Alessan’s excellent answer, here’s a video about the gun it was developed for. [![](https://img.youtube.com/vi/QGKcvM2Hh4g/maxresdefault.jpg "Kraut Space Magic: the H&K G11") ](https://www.youtube.com/watch?v=QGKcvM2Hh4g) ---
**Author:** ![mbh](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@mbh](https://boards.straightdope.com/u/mbh)\ **Post date:** [June 12, 2022, 2:52pm UTC](https://boards.straightdope.com/t/please-explain-bullet-sizes-for-guns-and-other-ammo-jargon/965964/42 "2022-06-12T14:52:32Z")
Interesting. An updated version of the Gyrojet. (Another solution in search of a problem.) > **[Gyrojet](https://en.wikipedia.org/wiki/Gyrojet)** > > Pages for logged out editors learn more > > The Gyrojet is a family of unique firearms developed in the 1960s named for the method of gyroscopically stabilizing its projectiles. Rather than inert bullets, Gyrojets fire small rockets called Microjets which have little recoil and do not require a heavy barrel or chamber to resist the pressure of the combustion gases. Velocity on leaving the tube was very low, but increased to around 1,250 feet per second (380 m/s) at 30 feet (9.1 m). The resu... ---
**Author:** ![RickJay](https://avatars.discourse-cdn.com/v4/letter/r/bb73d2/32.png) [@RickJay](https://boards.straightdope.com/u/RickJay)\ **Post date:** [June 12, 2022, 4:58pm UTC](https://boards.straightdope.com/t/please-explain-bullet-sizes-for-guns-and-other-ammo-jargon/965964/43 "2022-06-12T16:58:53Z")
> [@Whack-a-Mole](#): > > Where are there so many very minor variations on ammo? I assume you mean why, but in any event, within the various types of application, there actually aren’t as many variations as there really COULD be. A fairly limited number of possible ammunition types have become quite common, and make up most commonly used ammos, especially with the world’s militaries becoming very standardized for the sake of logistical efficiency. The immense popularity of 5.56mm ammunition in the Western world is the most obvious example, and prior to that you had the 7.62mm standard. ---
**Author:** ![ExTank](https://avatars.discourse-cdn.com/v4/letter/e/35a633/32.png) [@ExTank](https://boards.straightdope.com/u/ExTank)\ **Post date:** [June 12, 2022, 8:47pm UTC](https://boards.straightdope.com/t/please-explain-bullet-sizes-for-guns-and-other-ammo-jargon/965964/44 "2022-06-12T20:47:01Z")
> [@Whack-a-Mole](#): > > Where are there so many very minor variations on ammo? > > If you were designing a gun isn’t it better to conform to existing ammo? And, if not, then have a really compelling case for a wholly new ammunition size? To add to what **RickJay** said: arms and ammunition manufacturers aren’t much different than auto manufacturers in that they have marketing and sales departments, too. And some round and firearm offerings are marketing-driven, trying to garner a slightly bigger slice of the market with some advertising hype. Glock’s marketing and sales departments basically put Glock on the map, by offering great deals to law enforcement agencies all over the world. Didn’t hurt that they actually make a good firearm. Once they had the cachet of being the go-to law enforcement firearm, the civilian sales followed. ---
**Author:** ![jnglmassiv](https://avatars.discourse-cdn.com/v4/letter/j/f07891/32.png) [@jnglmassiv](https://boards.straightdope.com/u/jnglmassiv)\ **Post date:** [June 12, 2022, 9:31pm UTC](https://boards.straightdope.com/t/please-explain-bullet-sizes-for-guns-and-other-ammo-jargon/965964/45 "2022-06-12T21:31:49Z")
> [@running\_coach](#): > > … here’s a video about the gun it was developed for. That thing is nuts. The action looks like grandpa’s watch movement. ---
**Author:** ![GaryM](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garym/32/241_2.png) [@GaryM](https://boards.straightdope.com/u/GaryM)\ **Post date:** [June 13, 2022, 12:35am UTC](https://boards.straightdope.com/t/please-explain-bullet-sizes-for-guns-and-other-ammo-jargon/965964/46 "2022-06-13T00:35:01Z")
Don’t forget the case less, and “primer less” .22 rifle made by Daisy of air rifle fame. It used a case less round that was ignited by a jet of hot air created by the spring piston mechanism of an air rifle. [Daisy VL Rifle](https://en.wikipedia.org/wiki/Daisy_V/L) The ammo unfortunately tended to fall apart during normal handling. ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [June 13, 2022, 12:56am UTC](https://boards.straightdope.com/t/please-explain-bullet-sizes-for-guns-and-other-ammo-jargon/965964/47 "2022-06-13T00:56:48Z")
> [@jnglmassiv](#): > > That thing is nuts. The action looks like grandpa’s watch movement. It is actually pretty clever, especially the floating action that fires three rounds before the operator senses recoil. However, I would never want to carry that thing onto a battlefield, or even out to the range in moderately dusty or damp conditions. > [@GaryM](#): > > The ammo unfortunately tended to fall apart during normal handling. That is a general problem with caseless ammunition (in addition to all of the other issues that @Alessan described). With cased ammo you can drop it, kick it, jam it into magazines, throw it at your buddy, use the tip to clean your ear or change your gas port to “suppressed” in lieu of cleaning it, et cetera. With caseless ammo, if you look at it funny it cracks or melts. Some proposals have actually had ammunition coming in sealed, disposable magazines which I’m sure ammo manufacturers would love because US$100 for a stick of 50 rounds is a sweet deal for the seller. Stranger ---
**Author:** ![running\_coach](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/running_coach/32/15836_2.png) [@running\_coach](https://boards.straightdope.com/u/running_coach)\ **Post date:** [June 13, 2022, 1:13am UTC](https://boards.straightdope.com/t/please-explain-bullet-sizes-for-guns-and-other-ammo-jargon/965964/48 "2022-06-13T01:13:07Z")
> [@Stranger\_On\_A\_Train](#): > > With cased ammo you can drop it, kick it, jam it into magazines, throw it at your buddy, **use the tip to clean your ear** or change your gas port to “suppressed” in lieu of cleaning it, et cetera. - Isn’t that what those wings next to the front sight are for? ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [June 13, 2022, 1:14am UTC](https://boards.straightdope.com/t/please-explain-bullet-sizes-for-guns-and-other-ammo-jargon/965964/49 "2022-06-13T01:14:25Z")
You must have some big ear canals and a terminally poor sense of self-preservation. Stranger ---
**Author:** ![JRDelirious](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jrdelirious/32/9531_2.png) [@JRDelirious](https://boards.straightdope.com/u/JRDelirious)\ **Post date:** [June 13, 2022, 2:43am UTC](https://boards.straightdope.com/t/please-explain-bullet-sizes-for-guns-and-other-ammo-jargon/965964/50 "2022-06-13T02:43:56Z")
> [@Stranger\_On\_A\_Train](#): > > > [@jnglmassiv](#): > > > > That thing is nuts. The action looks like grandpa’s watch movement. > > It is actually pretty clever, especially the floating action that fires three rounds before the operator senses recoil. However, I would never want to carry that thing onto a battlefield, or even out to the range in moderately dusty or damp conditions. Ian always is a good source for those sorts of things – and this is an example of how all those round variations arise. NATO decides it needs a weapons system that’s light and shoots fast hot ammo, that lets each trooper carry a f\*\*kton of rounds. Some designers at an arms maker say to themselves “just making a slight variation on what exists is lame” and take it as a clue to try to create _their_ engineer’s dream Wonder Weapon/ammo combination. ---
**Author:** ![bump](https://avatars.discourse-cdn.com/v4/letter/b/7c8e57/32.png) [@bump](https://boards.straightdope.com/u/bump)\ **Post date:** [June 13, 2022, 2:53am UTC](https://boards.straightdope.com/t/please-explain-bullet-sizes-for-guns-and-other-ammo-jargon/965964/51 "2022-06-13T02:53:44Z")
Interestingly enough, those cartridges more or less go from right to left in terms of when they were adopted by their various militaries. There are exceptions though. ---
**Author:** ![DesertDog](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/desertdog/32/11503_2.png) [@DesertDog](https://boards.straightdope.com/u/DesertDog)\ **Post date:** [June 13, 2022, 7:34am UTC](https://boards.straightdope.com/t/please-explain-bullet-sizes-for-guns-and-other-ammo-jargon/965964/52 "2022-06-13T07:34:25Z")
> [@Stranger\_On\_A\_Train](#): > > often it is just someone trying to come up with some theoretically optimized ballistics that aren’t actually an improvement in the real world. [![](https://imgs.xkcd.com/comics/standards.png) ](https://imgs.xkcd.com/comics/standards.png) _Fortunately the charging one has been solved now that we have all standardized on mini-USB. Or is it micro-USB? Shit._ ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [June 13, 2022, 12:33pm UTC](https://boards.straightdope.com/t/please-explain-bullet-sizes-for-guns-and-other-ammo-jargon/965964/53 "2022-06-13T12:33:28Z")
> [@DesertDog](#): > > _Fortunately the charging one has been solved now that we have all standardized on mini-USB. Or is it micro-USB? Shit._ > **[EU agrees all phones and tablets must have a common charger by 2024](https://www.euronews.com/next/2022/06/07/eu-agrees-all-mobile-phones-tablets-must-have-the-same-charging-port-in-world-first)** > > Apple will have to change the connector on iPhones sold in Europe by 2024. ---
**Author:** ![thelurkinghorror](https://avatars.discourse-cdn.com/v4/letter/t/7c8e57/32.png) [@thelurkinghorror](https://boards.straightdope.com/u/thelurkinghorror)\ **Post date:** [June 13, 2022, 5:14pm UTC](https://boards.straightdope.com/t/please-explain-bullet-sizes-for-guns-and-other-ammo-jargon/965964/54 "2022-06-13T17:14:54Z")
> [@ParallelLines](#): > > ETA - this is actually why a large segment of gun owners consider 5.56 of AR-15 fame to be terrible home defense weapons, sure, lots of rounds, lots more range than a pistol, but dear god 5.56 is a nightmare of overpenetration scenarios unless you’re defending a multi-acre range/farm all by yourself. Lots of people say it’s actually ideal because it’s about 1/3 the weight of e.g. 9mm and gets its power from velocity, which is more dramatically slowed by walls and such. It will penetrate a drywall wall easily, but loses velocity by the time it would get to a neighbor’s house. I have zero personal experience or knowledge, but it seems to have some accuracy. ---
**Author:** ![thelurkinghorror](https://avatars.discourse-cdn.com/v4/letter/t/7c8e57/32.png) [@thelurkinghorror](https://boards.straightdope.com/u/thelurkinghorror)\ **Post date:** [June 13, 2022, 5:26pm UTC](https://boards.straightdope.com/t/please-explain-bullet-sizes-for-guns-and-other-ammo-jargon/965964/55 "2022-06-13T17:26:31Z")
Sometimes a caliber has both a metric and inch name, and it’s used differently in different countries. .32 ACP is 7.65×17mmSR Browning / 7.65 mm Browning Short pretty commonly in Europe. .380 ACP is 9×17mm Browning / 9x17mm Kurz (Short). But 9mm Luger / Parabellum is always metric no matter where you are. The names don’t often make sense, e.g.: Some of these numbers are rounded, .30 means exactly .308 inches. .30-06 - 0.3 caliber bullet, invented in 1906 .45-70 - 0.45" caliber, originally had 70 grains (4.56 grams) black powder, but now uses differing amounts of smokeless powder. Same with .30-30 and so on. .25-06 - a .30-06 case was squished at the neck to accept a .25 bullet. .22-250 - .22 bullet, 250 means that they took a .250-3000 Savage round and necked it down to .22 .250-3000 Savage - .25, about 3000 feet/second velocity when originally made .38 Special - .357", who TF knows. They also make rifles in .223 Wylde. You _will not find this ammo_, but it’s a rifle chambering that is made to accept both .223 and 5.56 while preserving any accuracy loss you might see from .223 in a 5.56 chamber. Also, .308 and 7.62x51 are similarly interchangeable civilian / military cartridges. But it’s the “opposite,” you can shoot 7.62 in a .308 rifle, but .308 may or may not be safe in a 7.62 rifle. ---
**Author:** ![silenus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/silenus/32/166_2.png) [@silenus](https://boards.straightdope.com/u/silenus)\ **Post date:** [June 13, 2022, 5:31pm UTC](https://boards.straightdope.com/t/please-explain-bullet-sizes-for-guns-and-other-ammo-jargon/965964/56 "2022-06-13T17:31:13Z")
> [@thelurkinghorror](#): > > .380 ACP is 9×17mm Browning / 9x17mm Kurz (Short). But 9mm Luger / Parabellum is always metric no matter where you are. _Everybody_ produced something in 9mm. Don’t forget the 9x18mm Makarov the Russians used. All the same caliber, yet totally different case lengths and loadings. (Yes, yes. The Makarov has a slightly larger bullet - 9.27 as opposed to 9.017.) ---
**Author:** ![running\_coach](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/running_coach/32/15836_2.png) [@running\_coach](https://boards.straightdope.com/u/running_coach)\ **Post date:** [June 13, 2022, 5:31pm UTC](https://boards.straightdope.com/t/please-explain-bullet-sizes-for-guns-and-other-ammo-jargon/965964/57 "2022-06-13T17:31:35Z")
> [@thelurkinghorror](#): > > Lots of people say it’s actually ideal because it’s about 1/3 the weight of e.g. 9mm and gets its power from velocity, which is more dramatically slowed by walls and such. **It will penetrate a drywall wall easily,** but loses velocity by the time it would get to a neighbor’s house. I have zero personal experience or knowledge, but it seems to have some accuracy. 6 walls(12 sheets of drywall). Still moving after 12 .75 inch pine boards. > **[The Box O' Truth #1 - The Original Box O' Truth](https://www.theboxotruth.com/threads/the-box-o-truth-1-the-original-box-o-truth.278/#post-1272)** > > This is the Box. > > Having some time for study of this fascinating sport, I built the "Box O' Truth". > > The purpose of the Box is to test the penetration of various rounds. > > People often say, "I think...". "I suppose...", "I bet...", when discussing... ---
**Author:** ![ParallelLines](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/parallellines/32/3575_2.png) [@ParallelLines](https://boards.straightdope.com/u/ParallelLines)\ **Post date:** [June 13, 2022, 5:54pm UTC](https://boards.straightdope.com/t/please-explain-bullet-sizes-for-guns-and-other-ammo-jargon/965964/58 "2022-06-13T17:54:31Z")
> [@thelurkinghorror](#): > > Lots of people say it’s actually ideal because it’s about 1/3 the weight of e.g. 9mm and gets its power from velocity, which is more dramatically slowed by walls and such. It will penetrate a drywall wall easily, but loses velocity by the time it would get to a neighbor’s house. I have zero personal experience or knowledge, but it seems to have some accuracy. In the sentence immediately prior to the one you quoted, I said the following: > [@ParallelLines](#): > > Again, +P and it’s ilk is part of the more is better. Most of the time… I don’t think so. My (and many other home defense planners) think the biggest issue isn’t penetration, it’s OVERPENETRATION. I don’t want to shoot (at all TBH first) and have a round go astray across the street / through the wall / up and out. And even a 9mm will do this. So yes, I am clear that a 9mm can be dangerous in the exact same way. The number of quality expanding rounds for reduced penetration in modern defensive ammo is helpful, but not a magic bullet (pun intended) by any means [[Glaser](https://en.wikipedia.org/wiki/Glaser_Safety_Slug) being my favorite ]. But I still find the 5.56, with it’s higher base range a much bigger risk than 9mm, and only recently has that round begun to have the same sort of tricks to offset it. So basically, both are dangerous for ‘in-house’ shootings, with the 5.56 having some additional risks for shoots near exterior walls. All guns are dangerous for the entire range of their flight, so always be mindful of what is behind your target. For the OP, and anyone who doesn’t want to click the link, Glaser rounds are an ammunition variant designed initially for pistols that attempt to minimize the risks of penetration by replacing the traditional bullet structure with a compressed body surrounding a core of fine shot, with a polymer cap. Basically, designed to fragment upon contact with target (serious wounds) or a barrier (thus reducing chance of penetration). For my personal view on defensive loading for a carry weapon, feel free to click to expand below, not really appropriate to the thread’s purpose and don’t want to hijack further. > **Summary** > > When I carried, I had a S&W 9c with a 12 round magazine. First 8 were Glaser, last 4 were +P Hornady JHP (jacketed hollow points). The intent was that the if ever (powers that be avert) I was forced to shoot I’d minimize the risks of penetration and maximize the chance to put my attacker down. And if I was in a situation where I for some god-forsaken reason needed to penetrate, the last few rounds had a slightly improved chance. > > I use a similar load out for my home defense pistol in the biometric safe, and my wife’s .38 special is loaded with nothing but glaser blue tip. ---
**Author:** ![thelurkinghorror](https://avatars.discourse-cdn.com/v4/letter/t/7c8e57/32.png) [@thelurkinghorror](https://boards.straightdope.com/u/thelurkinghorror)\ **Post date:** [June 13, 2022, 5:59pm UTC](https://boards.straightdope.com/t/please-explain-bullet-sizes-for-guns-and-other-ammo-jargon/965964/59 "2022-06-13T17:59:36Z")
Yes, other analyses have shown different, I’m repeating what may just be lore, but it’s a common argument. Note that this is a FMJBT bullet. You should not be using that in any reasonable self-defense situation, whether at home or outside. Exceptions are very small pistol calibers where HP doesn’t seem to work well. ---
**Author:** ![silenus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/silenus/32/166_2.png) [@silenus](https://boards.straightdope.com/u/silenus)\ **Post date:** [June 13, 2022, 6:11pm UTC](https://boards.straightdope.com/t/please-explain-bullet-sizes-for-guns-and-other-ammo-jargon/965964/60 "2022-06-13T18:11:14Z")
> [@ParallelLines](#): > > For my personal view on defensive loading for a carry weapon, feel free to click to expand below, not really appropriate to the thread’s purpose and don’t want to hijack further. Not really a hijack, since it deals with different loads. My home defense weapons are sequentially loaded the same way. The pistol in the nightstand is a S&W Model 28 Highway Patrolman .357. The loadings are: .38 Special wadcutter, 2 .38 Special soft nose, .38 Special +P JSP, 2 .357 JHP. 4 different loads, 4 different bullets, 2 “different” calibers - all in the same revolver. [Previous page](https://boards.straightdope.com/t/please-explain-bullet-sizes-for-guns-and-other-ammo-jargon/965964.md?page=2) [Next page](https://boards.straightdope.com/t/please-explain-bullet-sizes-for-guns-and-other-ammo-jargon/965964.md?page=4)