Caliber questions

[InspectorCallahan]

Hi all! Just joined the forum after seeing advertisements at the gun show in Richmond yesterday. By way of introduction, I'm a newbie to the gun scene, but have been reading and researching extensively. I'm a member of the NRA and have a CHP, and just purchased my first handguns in the last couple of months (Ruger SR9c and LCP).

I'm curious about calibers and ammo ratings. Here are my questions:

1. What is the difference between a .38 and a .380? I know they're very different, but the number is the same, no matter how many zero's you add.
2. Why is there both a .44 and a .45? Why not a .43 or a .46? How do they differ?
3. Why do they call a .38 a ".38 Special"? Why not just call it a .38? Are all .38's "Specials"?
4. What's the difference between a .44 and a .44 Magnum, or .357 and .357 Magnum? Why is there a Magnum for these two calibers and not all other calibers?
5. Why did they make a .357? Why not just a .36? Why three digits?
6. Why do they call a .380 ".380 auto"? Why not just ".380"?
7. Why do they refer to 9mm as "9 X 19"?
8. I understand a 9mm is basically the same as a .380. So why have both calibers, and why not just call the .380 a "9mm short"?
9. I understand a .38 is the same diameter as a .357. So why are they labeled differently and why do we need both?
10. How does "grain" get measured? By the amount of gun powder in a round, or its weight, or something else? How does one know what grain to use? I see very different grain numbers depending on the caliber. Like, in .380, I see 80 or 90, and in 9mm I see the numbers up in the hundreds.
11. Beyond grain measurement, I don't understand the "+P" rating. How does the +P ammo become +P? Is it packed tighter, is there more powder, is it different in its compounding, or what?

Thanks to all who respond.

InspectorCallahan

[wally626]

Hi all! Just joined the forum after seeing advertisements at the gun show in Richmond yesterday. By way of introduction, I'm a newbie to the gun scene, but have been reading and researching extensively. I'm a member of the NRA and have a CHP, and just purchased my first handguns in the last couple of months (Ruger SR9c and LCP).

I'm curious about calibers and ammo ratings. Here are my questions:

.......

Thanks to all who respond.

InspectorCallahan

I'll try my beginners gun knowledge out.

The answer really comes down to the fact that whomever develops the cartrige gets to name it. Sometimes they want a different sounding name. The 10mm and .40S&W are very similar the .40%&W being shorter with less power. They could have named it the 10mm short but did not. 9mm is a very popular size round but it has many variations that need different names so over time various shorthand and trademakrded names have evaloved. The normal 9mm round that most peopel use can be called the 9mm Parabellum (after the bullet chape) the 9mm Luger (after the most popular gun that shot it) or the 9x19mm. The .38 was originally named after the case diameter prior to most ammunition using the bullet diameter. There is a .38 caliper that is actucally .40 diameter. American developed rounds tend to have english units and continental Europe metric.

See http://en.wikipedia.org/wiki/Caliber for a list of common calipers.

[wally626]

10. How does "grain" get measured? By the amount of gun powder in a round, or its weight, or something else? How does one know what grain to use? I see very different grain numbers depending on the caliber. Like, in .380, I see 80 or 90, and in 9mm I see the numbers up in the hundreds.
11. Beyond grain measurement, I don't understand the "+P" rating. How does the +P ammo become +P? Is it packed tighter, is there more powder, is it different in its compounding, or what?

A grain is 1/7000 of a pound, it is not the size of the actual chunk of gunpowder. Normally in ammunition the grain listed is the weight of the bullet not the amount of gunpowder but some ammunition lists both. The amount of gunpowder used varies with the exact type of powder being used, so to know a round has 7 grains of powder does not tell you much unless you know the specific type used.

+P means the round is loaded with enough gunpowder (of whatever type and quantity) to raise the chamber pressure to a level above the typically design level for the round. It is a known amount and some guns are designed to be used with +P ammunition others are not. +P+ implies the loading is hotter than +P but is unspecified and is not a particular standard.

There is a standards body that regulates these things, but I have forgot the acronym.

[Vahunter]

A good reloading manual will answer just about your questions.

[InspectorCallahan]

Wally -

I'm still confused about grain. You stated it's usually not the amount of gunpowder, but the weight of the bullet. But, many people when they talk about grain say that a particular grain is too "hot", which tells me grain isn't referring to the bullet. Bullet size wouldn't have anything to do with heat like the amount or mill of the powder would. Given that knowing the grain number doesn't help if you don't know what the type of gunpowder used was, why even publish it on the box (I imagine that's required of the manufacturer, but it still doesn't really inform you).

Now, if a grain is 1/2000th of a pound, that would make an 80 grain bullet 80/2000th of a pound. That would mean it would take 25 of them to make a pound. There is no way 25 cartridges of 80 grain would make a pound of gunpowder, so in that case it must be referring to the bullet weight. Even there, I don't see 25 bullets making a pound. And it seems like most manufacturers have specific grains they want you to use, but I can't imagine they care about the bullet weight as much as they do the gunpowder quantity/type/pressure/etc.

So, I'm still very lost on this issue. But thanks for your input.

Inspector

[SgtBill]

My friend you will stay confused unless you get a good reloading manual to read. A manual will answer all your questions such as a .380 is a 9 MM short, parabellum stands for made for war, 38 spl. is a shorter case and less power then a .357 magnum and a .357 magnum won't fit in a .38 spl. revolver but a 38 spl. will fit in a .357 magnum. The first 38 was a short round that carried a bullett of about 200 grains then the 38 spl. was made with a longer case and more powder room with a normal slug of 158 grain round nose lead. Etc,Etc.
Bill

[Vahunter]

Grain is a weight. For example I just finished reloading some .45ACP's. I used 4.5 grains of Titegroup powder and a 230 grain bullet. Hope that helps.

[gunderwood]

Hi all! Just joined the forum after seeing advertisements at the gun show in Richmond yesterday. By way of introduction, I'm a newbie to the gun scene, but have been reading and researching extensively. I'm a member of the NRA and have a CHP, and just purchased my first handguns in the last couple of months (Ruger SR9c and LCP).

I'm curious about calibers and ammo ratings. Here are my questions:

1. What is the difference between a .38 and a .380? I know they're very different, but the number is the same, no matter how many zero's you add.
2. Why is there both a .44 and a .45? Why not a .43 or a .46? How do they differ?
3. Why do they call a .38 a ".38 Special"? Why not just call it a .38? Are all .38's "Specials"?
4. What's the difference between a .44 and a .44 Magnum, or .357 and .357 Magnum? Why is there a Magnum for these two calibers and not all other calibers?
5. Why did they make a .357? Why not just a .36? Why three digits?
6. Why do they call a .380 ".380 auto"? Why not just ".380"?
7. Why do they refer to 9mm as "9 X 19"?
8. I understand a 9mm is basically the same as a .380. So why have both calibers, and why not just call the .380 a "9mm short"?
9. I understand a .38 is the same diameter as a .357. So why are they labeled differently and why do we need both?
10. How does "grain" get measured? By the amount of gun powder in a round, or its weight, or something else? How does one know what grain to use? I see very different grain numbers depending on the caliber. Like, in .380, I see 80 or 90, and in 9mm I see the numbers up in the hundreds.
11. Beyond grain measurement, I don't understand the "+P" rating. How does the +P ammo become +P? Is it packed tighter, is there more powder, is it different in its compounding, or what?

Thanks to all who respond.

InspectorCallahan

Welcome. Here are quick answers to your questions, but I recommend you read up. Better yet, come out to the shoot and greets. You probably try them all and have a great time too. Also, a good reloading book will answer these. Hornady's has a brief cartridge history section, but a lot of others do too.

1. First thing is that naming convention doesn't mean jack squat. It is just a name, nothing more. For example, I assume you mean .38 Special. The max outside measurement of the brass .379", but the bullet is only .357". .380Auto (also called 9mm kurz, 9x17mm, etc.) is .373" and .355" respectively. .357Mag on the other hand actually shoots a .357" bullet, while 9mm shoots a .355". See, names are just marketing in lots of cases. That aside, I think the intent of your question is what the practical differences are. .38 Special is generally a revolver cartridge, while 380 auto is a semi-auto cartridge. The .38 Special is marginally more powerful than the 380auto, but neither of these would be considered a powerful handgun cartridge, but it depends on what you are using them for. These two rounds are commonly used in small self-defence pistols or the recoil sensitive. Before anyone jumps on me, that doesn't make them bad, just different.

2. Why do we make so many different car engines? Because we can and people want different things. Bullet size is only one small aspect of a cartridge. 380auto, 9mm, and .357SIG all shoot the same diameter of bullet, but they are very different rounds. Kind of like saying all cars with 18" rims are the same why would anyone make 17"s or 19"s, etc.

3. Marketing and slang. See #1. It can get much worse (or better depending on how you look at it) when you have virtually identical rounds with different qualification ratings, like 9mm Luger and 9mm NATO or .308Win and 7.62x51mm or .223Rem and 5.56x45mm (they are not the same, that is why I said virtually).

4. Magnum generally means larger case, which allows for more powder and consequently a more powerful round. Lots of the new magnums are marketing only.

5. Naming again, but there is something too it. Three digits is easily measurable with a decent tool and happens to be relevant to creating safe ammo. The difference between .45" and .44" is enough that I could blow a gun up, while a difference between .4501" and .4500" is irrelevant in nearly all cases. The .45 you are use to is actually .451", but it gets into the naming/marketing thing again. Have you ever looked up how many cu in or CCs your car engine actually is? Yup, in nearly every case they rounded it. Same here. 3.6L sounds better than 3547 CCs.

6. The automatic rounds are very different in design than the revolver rounds. Some times it is left off, other times it isn't. E.g. .45 is not exclusive to but often is referring to .45Auto/.45ACP (Automatic Colt Pistol). Depends on the cartridge. Sometimes it is slang, other times there are real differences. If you are catching the car comparison, you should get my drift.

7. The first number is the diameter of something (brass, bullet, bore are common) and the second is the brass length. E.g. 9x19 (also called 9mm Luger, 9mm Parabellum, 9mm NATO, which are and aren't identical) shoots a 9mm bullet (9mm/25.4mm/in = .35433" which rounds to .355" in this case and yes I know that isn't actually the correct way to round). The brass is 0.754", which happens to be pretty close to 19mm.

8. 380 is basically half the cartridge 9mm is as measured by energy. 9mm recoil would be much harsher too (thank you Newton). Hornady says 380 will push their 100gr bullet to 900-950fps, while 9mm will push the same bullet about 1300fps. Lots of companies make 3.6L (or very similar) V6 engines right now or how about 1.4-1.7L inline fours. Why don't they all use the same engine? There is a lot more to consider besides engine volume capacity and the same is true with cartridges. I have a rifle chambered in .338 Lapua Mag. Technically the bore diameter is smaller than either 380 or 9mm (.338" vs. .355"), but heaven help you if you tried to fire that thing in a handgun! It is only at least 10x more powerful than the hottest 9mm or .45. Without a muzzle break on your rifle it can actually hurt you (like detached retinas). Bore size is only one measurement...

9. A lot of economy cars have 1.5L inline fours and formula 1 use to run a 1.5L inline four. Before they changed the engine spec everyone had to use, BMW built a 1.5L inline four that maxed their dyno. The dyno was rated for 1200HP. Best guess is the engine made somewhere between 1300HP and 1500HP. They did have one on display in the SC plant. The engine only made that power in qualifying trim, IIRC was 900+ in race form. Why do we need two engines with 1.5L capacity?

10. The grain we use today is a unit of mass (not weight!), just like grams. It has been around long before real firearms. Grains are used because we aren't in Europe and they happen to be relevant to firearm measurements (the scale of measurements needed. E.g. you wouldn't use tons to measure a single feather, it would be too cumbersome). Metric reloading data, like Lapua/Vihtavuori) use grams.

11. Cartridges have specifications. Cartridges that are sold commercially usually follow the SAMMI or CIP specs. This insures that when you buy a bullet it should work in your gun; also liability reasons. One of these specs is the max pressure (PSI). +P means that this cartridge will exceed the standard pressure, but not the +P limit. There is also a +P+ rating which is even higher. Generally, these ratings are found on older cartridge designs. When something like .38Special or 9mm or .45Auto was speced, the guns couldn't safely handle higher pressures (or just weren't speced that way). With more modern firearms which use stronger materials, there was a desire to exceed the standard pressures for more performance. Thus, +P and +P+ ratings were created. For example, 9mm Luger is 35k PSI, 9mm +P is 38.5k PSI, 9mm NATO is 37k PSI. You shouldn't fire a +P or +P+ round in a gun that isn't rated for it. Even those that are, wear and tear is accelerated. More modern cartridges, like .357SIG and .40SW, have their standard pressures often higher than the older ones even with +P or +P+. IIRC 9mm +P is 38.5k PSI and .357SIG is 44k PSI. +P ratings are one of the gun worlds way of boring out cylinders, nitrous, turbo/super chargers, etc.

[Vahunter]

Number 10 would be true if you were measuring crops such as wheat, barley and oats. Or blackpowder by volume which is the most of us measure it. But in the ammo world it's a weight. My Lyman electronic scales can be programed to weigh in grains, grams and ounces. Doesn't say anything about mass.

[gunderwood]

Number 10 would be true if you were measuring crops such as wheat, barley and oats. Or blackpowder by volume which is the most of us measure it. But in the ammo world it's a weight. My Lyman electronic scales can be programed to weigh in grains, grams and ounces. Doesn't say anything about mass.

And they would be wrong. Mass and weight are not the same thing and grain is defined as mass, specifically 1 grain = 64.79891mg. They probably say weight because to the layman they are the same thing.

http://en.wikipedia.org/wiki/Grain_(mass)


Mass is a measurement pertaining to the amount of matter in something, while weight is the gravitational "pull" between two masses. For example, a 125 gain projectile is 125 grains even if it is on the moon. However, the weight of it changes. I.e. if you used a digital scale to measure it, the weight would be less than measured on earth. It should be noted that a balance beam scale is not affected since both the mass being measured and the mass used to balance it would both experience the same effect of reduced gravity. Same with the men who walked on the moon.

http://en.wikipedia.org/wiki/Mass_versus_weight

As the article notes, digital scales and the like actually show a difference in measured weight of approx. 0.5% between the equator and the poles. Mass equates to weight only with the assumption of a gravitational constant. In our case we call it standard gravity and it is 9.80665 m/s^2.

[wally626]

Wally -

I'm still confused about grain. You stated it's usually not the amount of gunpowder, but the weight of the bullet. But, many people when they talk about grain say that a particular grain is too "hot", which tells me grain isn't referring to the bullet. Bullet size wouldn't have anything to do with heat like the amount or mill of the powder would. Given that knowing the grain number doesn't help if you don't know what the type of gunpowder used was, why even publish it on the box (I imagine that's required of the manufacturer, but it still doesn't really inform you).

Now, if a grain is 1/2000th of a pound, that would make an 80 grain bullet 80/2000th of a pound. That would mean it would take 25 of them to make a pound. There is no way 25 cartridges of 80 grain would make a pound of gunpowder, so in that case it must be referring to the bullet weight. Even there, I don't see 25 bullets making a pound. And it seems like most manufacturers have specific grains they want you to use, but I can't imagine they care about the bullet weight as much as they do the gunpowder quantity/type/pressure/etc.

So, I'm still very lost on this issue. But thanks for your input.

Inspector

Its 1/7000 so it takes 87.5 80 grain bullets to make a pound of mass. I am not sure what they refer to as a hot grain. There are hotter powders than others, so it would take less grains of powder to reach a given chamber pressure. Also some people refer to a grain of gunpowder in the sense of the little pieces not the weight, so it can get confusing. The performance of a particular ammunition is a function of the uniformity of the bullets, cases and of the powder load, so they care about all of the above. I have never been involved in ammunition production so i do not know which factor is held to a tighter tolerance during manufacture. In black powder ammunition it is more common to have the amount of powder listed, but for the normal ammunition you see on store shelves the grain number is the weight of the bullet. For example, I just picked up a box of ammo in my closet it is listed as .40S&W 180 grain FMJ. The first is the type of cartridge, and in this case also the bullet caliper, the mass of the bullet and finally the construction of the bullet, full metal jacket.

[Palladin]

Garrett, I think you should run the reloading class at SgtBill's! I'll be yer step and fetchit guy...

I really enjoyed this thread. I've often wondered myself -"Why so many?" I guess it's because we can. 'Cause I know with a .22LR, .45ACP, 30-06 and a 12Ga, one can take care of any kind of critter he might run into on this continent... We wouldn't have near as much to talk about though! - The auto analogies are spot on.

+1 on getting a reloading manual, even if just for the coffee table. The history of the metallic cartridge in general, and the specifics of individual cartridges and how they were developed is fascinating in itself.

[gunderwood]

Garrett, I think you should run the reloading class at SgtBill's! I'll be yer step and fetchit guy...

I really enjoyed this thread. I've often wondered myself -"Why so many?" I guess it's because we can. 'Cause I know with a .22LR, .45ACP, 30-06 and a 12Ga, one can take care of any kind of critter he might run into on this continent... We wouldn't have near as much to talk about though! - The auto analogies are spot on.

+1 on getting a reloading manual, even if just for the coffee table. The history of the metallic cartridge in general, and the specifics of individual cartridges and how they were developed is fascinating in itself.

You might change your mind when you see me stuffing 74.5gr of H4350 into a .300WSM case. It literally is a full case compressed load; I have to be careful to not spill it when rotating to the next station.

Taggure wants me to come to his place on the 5th for his birthday party instead of Bills. I keep telling him to have it down there, but he mutters something about family from out of town. Wasn't someone planing to do a reloading class already or were people just asking for one? I wouldn't mind doing it.

This is a good book with lots of pictures: http://www.amazon.com/Cartridges-World- ... 0873496051

OP: grain is a unit of mass, but since the gravity on earth is more or less constant for places we actually live, we mix it up with weight. The Kilogram is a unit of mass too, but we commonly perceive it as how heavy something is. If you don't understand this distinction, don't worry about it. Assume that a grain is a measurement of how heavy something is, for the measurements we are making it won't really change the results.

Bullet: You want to know how heavy it is, what bore size it is, construction and shape. E.g. 9mm bullets often range from 90-147grs, with the most common weights of 115gr, 124gr and 147gr. In general, the larger the bullet diameter is the heavier the average bullet will be. E.g. .45Auto bullets usually range from 185-230gr. Common bullet weights are 185gr, 200gr and 230gr. .40SW is between 9mm and .45Auto and its bullets commonly range from 155-180gr. It is possible to build different weight bullets by playing with their design and materials. These weight ranges are generally driven by bore diameter, common materials and our ability to stabilize the bullet, particularly for a rifle. Cartridge powder capacity also plays a role. E.g. .30 cal rifle bullets generally range from 110-240gr, but a .308Win can't push bullets past 190gr fast enough to make it worth it in most cases. However, .300WM can and the 220gr SMK is a great bullet for this cartridge. I like the 175SMKs in .308Win.

Powder: Just like bullets, you need a way of measuring how much to put in the case. Powders burn at different rates. Put a pistol powder in a rifle and you will probably blow it up (subsonic loads not withstanding). Since grain is our common measurement of "weight," we use that. Most semi-auto pistols will be around 4-7grs of powder. .308Win uses 40-45grs and .300WM can handle 70-75grs. Obviously, the use similar steels, so those rifle powders need to burn slower than the pistol or the peak pressure would blow them up. The rifles also have a longer barrel to allow the slower powder to burn completely (or close to it). A reloading manual will specify how much powder and what kind.

Brass and Primer: You can weight these too, but only the super serious guys go to this trouble.

Buy that book and it will answer most of your questions. A reloading manual will too.

[InspectorCallahan]

I guess I need to get a reloading manual! You guys are talking at a level way above my comprehension.

Thanks everyone.

InspectorCallahan

[gunderwood]

I guess I need to get a reloading manual! You guys are talking at a level way above my comprehension.

Thanks everyone.

InspectorCallahan

Nothing like hands on experience, come out to a greet and shoot.

[InspectorCallahan]

A "greet and shoot"... Talk about a newbie - I don't know anything about those, or where they're held!

InspectorCallahan

[Diomed]

I guess I need to get a reloading manual! You guys are talking at a level way above my comprehension.

Thanks everyone.

InspectorCallahan

Don't worry so much about the details. You don't need to know about how much and what kind of powder is in the case. What you do need to know is what kind of ammunition is safe and appropriate for whatever you're shooting. That done, you can focus on how to shoot safely and enjoyably.

You need to think grade school, not college. Start at the beginning, not the middle or the end. If you want to learn the nitty-gritty details, that's great - but get your foundational education taken care of first.

[Palladin]

http://vagunforum.net/meet-and-greet/cu ... t4395.html

and

http://vagunforum.net/meet-and-greet/cu ... t4240.html

[OakRidgeStars]

A "greet and shoot"... Talk about a newbie - I don't know anything about those, or where they're held!

InspectorCallahan

You can find information on upcoming events in the Meet & Greet section.

http://vagunforum.net/meet-and-greet/

Our next M&G is June 5 in Keysville. Hope you can make it.

[InspectorCallahan]

Diomed, yours was good advice. But I thought I was doing just that - starting with the basics. And I don't know one caliber from another, so I thought I ought to learn the differences. And I quickly got overwhelmed with confusion. Then the grain issue arose, and the +p, and the +P+. Mindboggling!

I'll have to check out a meet and shoot. It will have to be in the Richmond area. But first I need to get my training under my belt! I don't even want to put a bullet in the mag until then.

InspectorCallahan