My son asked me yesterday. I’m gun-ignorant by choice, and so I turn to the Teeming Millions. He asked me what makes a gun a Magnum.
I said, I thought it couldn’t just be size, because a standard Army .45 caliber ought to be bigger than a .357, or a .44 and both of those ( as any fan of Dirty Harry movies knows ) come as “Magnums”. I said perhaps the kind of bullet, but I admitted I know nothing about this topic.
What’s the Straight Dope?
Cartooniverse
A magnum round is a round containing a larger explosive round than other cartidges of the same size. A magnum firearm is a weapon designed to shoot the more powerful magnum round. Shooting a magnum round from an ordinary firearm is a dangerous no-no.
Make that “larger explosive charge”, not “larger explosive round.” One too many rounds in that sentence.
The 38 special will shoot in the .357 magnum. My wife and I shoot .357 pistols. She likes to target shoot the light loaded 38 spl. in her .357. I reload our ammo and I only need one size reloader. The only difference in the .357 magnum and the 38 spl is the length of the shell casing and of course the extra powder charge.
Basically a marketing term by now with no ``real’’ significance. Most cases are shaped sorta like a beer bottle, with the bullet crimped into the neck and a wider part that holds the gun powder. If you keep the same neck (and therefore bullet) diameter, but make the bulgy part of the cartridge either wider or longer than normal', then you've got a magnum cartridge that sends the bullet out faster, giving it a flatter trajectory and more energy down-range than the standard’ round of that caliber. Thing is, by now, there’s so many different cartridges out there for any given bullet caliber, that `magnum’ really no longer has a technical definition.
But with very few exceptions (and olefin hit one), you have to match not only the bullet diameter (e.g. 0.30 inches), but the entire cartridge description (e.g. 30-06 Springfield, or 308 Winchester, or whatever) to the chamber of the gun, or else truly bad things happen.
For the most part shooting a magnum round from a non-magnum firearm is impossible by design.
As an example the …44 Remington magnum was developed from the .44 S&W Special. The dimensions of the two cartridges are the same except the magnum has a longer case. The case is slightly larger in diameter than the bullet so there is a step in the chamber where the case ends. This prevents a .44 magnum catridge from being inserted into a .44 special chamber. .38 special and .357 magnum have a similar difference in case length. The bullets are the same diameter but the .38 designation was used for some historic reasons though the bullet is typically .357" in diameter. For those examples the mangum gun can fire non-magnum ammunition but magnum ammunition will not fit in a non-magnum gun.
There are some more technical differences. Magnum ammunition will typically use larger charge of a slower burning propellant than it’s non-magnum counterpart. Modern smokeless propellant powder is not an explosive. Old fashioned black powder is considered an explosive but a low order type.
Rifle ammunition is a different matter as “bottleneck” cartridges cannot have interchangable short and long versions. Having the correct length from the base to the shoulder of of the case is so critical that being a few thousandths of an inch too short can cause a case separation and possibly a catastrophic explosion of the gun.
There are examples of a standard and magnum version of the same caliber name but they are almost never interchangable. .222 Remington and .222 Remington magnum are simiar except for case length but are absolutely not interchangable.
Some magnum rifle cartridges have a belt around the base just ahead of the normal rim but this is done for a technical issue, headspacing. It became popular in the 20s and 30s with Holland and Holland calibers but is absent from recent magnum cartridge designs.
To clarify my last paragraph, .222 and .222 mag should not be interchanged but the design doesn’t always prevent it. A .222 cartridge could be put into a .222 magnum or .223 chamber but doing so is very, very, very bad. We’re talking the rifle reciever possibly exploding like a grenade. A .222 magnum cartridge could not be chambered in a .222 rifle.
Padeye knows a lot more about this stuff than I do, as I learned very quickly when I first started posting here. I hope he will be good enough to correct any errors I make here.
To answer the OP, the “magnum” designation is just marketing hype.
Sometime in the 1870’s, Smith & Wesson built revolvers on the Model 3 frame* for the Imperial Russian Army. The Russians didn’t like any of the then available calibrations, but they liked the gun. So S&W designed a new cartridge of nominal .44 caliber (not really .44 inches for the historical reasons Padeye alluded to) called .44 Russian. For obvious reasons.
Sometime in the 1890’s somebody had a brainstorm and began tinkering with the .44 Russian, and lenghthened the case to allow it contain more (black) powder. All other dimensions were left alone. The resultant cartidge was dubbed the .44 “Special,” because it was better than the .44 Russian. The progression from the .44 Special to the .44 Magnum is as described above.
Now, to actually answer your question. I’ve been told by folks at Remington that the term “magnum” was just a marketing tool to give the impression of more power. It’s supposed to be derived from Magnum champaigne (sp?) bottles. They’re bigger than the regular ones.
Really, where else can you go from “special.”
A similar progression happened with .38/.357 calibrations:
.38 S&W -> .38 Special -> .357 Magnum.
So, I guess the real question is, why isn’t the .44 Magnum called the .429 Magnum?
*These days, model numbers refer to distinct products, but at that time they just referred to frame size.
No errors I’m aware of Exgineer.
Not certain about the .44 designation of .427-429 bullets but it was in use a decade before the S&W Russian with the .44 Henry flat. I think it may have had to do with the heeled bullet which has the same diameter as the case body and a stepped heel like a .22 rimfire.
Colt fudged the other direction designating .44 caliber for C&B and early cartridge revolvers we would now call .45s as early as 1847 through 1872.
Your point about black powder is a good one. Black powder needs to be compressed with no air space in the case so the case size has a direct correlation to power. Modern smokeless propellants can be loaded “loose” and have more energy/mass so a tiny cartridge like a 9mm parabellum can have more power than a .38 special with a similar bullet.
Can you check me on something?
I always assumed that the difference between nominal calibers and actual calibers resulted directly from the conversion of caplocks to cartridge revolvers.
Like you said, the heel-type bullets were made to match the bores, but they did creative stuff like sleeving barrels to get a more modern cartridge configuration where the lubrication grooves are contained within the case.
I’ve always understood that that’s why “.44” is actually between .427 and .429.
I’ve heard the same arguement for .38’s, and I don’t get it. I cant find caplock .38 references no matter how hard I look.
Colt Navies were marketed and sold with the proper calibration stated. .36
Where did “.38” come from?
I’m going to let my son read this thread, it will more than answer his question. Thank you, for providing such thorough and concise information. You guys and gals rock. 
Exgineer, there are a lot of reasons for seemingly bizarre caliber designations and you’ll find them often misleading and inconsistent.
In Europe/UK it’s common to use the smaller bore/land diameter while the US uses the larger goove diameter. A US .308 Winchester in fact uses a .308" bullet but a .303 British uses a .311 bullet.
Some calibers are given arbitrary names by their inventors. Calibers that all use a .224" bullet are called everything from .221 Fireball to .225 Winchester… I think , don’t hacve my refernce manual handy. Remington called its 1858 C&B revolver a .45 though it had the same bore as a .44 Colt.
As I mentioned the .38 designation comes from the .36 cal C&B (caplock) revolvers like the Colt 1851 navy model. It used a .375" lead round ball or conical bullet and was later converted to .38 Colt cartridge. When the bullet design was changed and made smaller the same size case was used.
FWIW the only true .38 I know of is the .38-55 Winchester which uses a lead .379" bullet. It’s used in some lever action and single shot rifles.
U.S. standard is bore diameter, euorpean standard is land diameter. Got it.
That’s what I wanted to know, and I apologize for making you say it twice.
I need to work on that “reading comprehesion” thing.
It would be difficult to point to another field of technology with a less organized terminology than the science/art of small arms and ballistics design. While there are discernible, limited patterns in the naming of calibers, the patterns are definitely the exceptions; chaos is the rule.
As to the OP, the term “magnum” has been overused and frivolously applied to the point of becoming meaningless. If, for example, it means a larger or more powerful version of an existing round, then who can explain the “magnum” rounds that are based on no other? (Witness the Weatherby line of rifle magnums and the .41 Mag handgun cartridge.)
Firearm calibers derive their names from sources as diverse as their creators. Some reflect actual caliber, or diameter, like the .243 Winchester. Some refer more to the creator, like the .454 Casull. Some are based on black powder capacity, like the .45-70 and the .30-30. Others, like the .250-3000 Savage, combine factors like caliber of bullet, advertised muzzle velocity and gunmaker. Still others are “standardized” wildcat rounds that may be designated any way – the .22-250, for instance, is a round that fires a .22-caliber bullet from a case that was modified from the older .250-3000 Savage. Some reflect a company name that either designed or initially marketed the round – .222 Remington, .308 Winchester, .40 S&W, .32 H&R Magnum. Even closely-followed designations can be misleading; every modern .44 caliber cartridge (there are at least half a dozen) is actually barely .43 caliber (.429"). Still others are meaningless numerical variations, like the .222 Remington and the .223 Remington, which are both .22 caliber rounds that use interchangeable bullets but cannot be chambered in the same gun; the .223 is a newer version of the .222 with a longer case. Padeye mentioned the wild variation of “.22 caliber” rounds, but I think he forgot that it goes as low as the .218 Bee, which uses the same bullet diameter (.224") as the .225 Winchester.
I guess my point is that “magnum” has little logical meaning, as is the case with most caliber designations.
T-Bone’s struck the nail squarely.
Part of the problem is some of these calibers have been in existence for a century or more, and some have their roots encompassing three, maybe four generations of technology (flintlock, cap-and-ball, metallic blackpowder, metallic smokeless, etc.)
The .44-40, for example, was a .44 cal case that held 40 grains of blackpowder. Same with the .45-70 and the .50-70, but the .30-'06 of a couple generations later is entirely different. It’s a .30 (actually .308") caliber adopted by the Military in 1906.
In simplest terms, Toony, “magnum” was a derivation, as noted above, of a lengthened version of a previously-existent cartridge.
The .38 S&W (technically the .38 Short) was lengthened to hold more powder, and called the .38 Special. The Special was lengthened again to hold yet more powder, and thus dubbed the “Magnum”.
The .357 Magnum- the first cartridge so named- proved to be such a popular round, that the monicker “magnum” became an instant marketing gimmick- the .44 was stretched and became the .44 Magnum. The .22 Long Rifle (itself stretched from the Long, which came from the .22 short) was lengthened and immediately dubbed the .22 Magnum.
After that, everything became a “magnum”. The .41 (which had few, if any, antecedents) for example, and in the past 20 years or so, we’ve seen .45 Winchester Magnum (a stretched .45 ACP) any number of rifle cartridges were relabeled Magnums, and there have been a whole passel of rounds that didn’t quite make it, such as the .451 Detonics Magnum (another souped-up .45 ACP) the 9mm Winchester Magnum (the .45 WinMag necked down to take .355" bullets) and so forth, ad nauseum.
So in the beginning, when it was first used, it technically meant a cartridge that had been stretched out for additional power, from a previously-extant round.
Now, of course, it’s just marketing buzz.
FWIW the .30-30 was not a black powder round but used the BP naming convention anyway. The .427" diameter 44-40’s smaller cousin .38-40 had a .401" diameter bullet. I’ve heard no good explanation other than it means 38 grains BP and a .40 bore.
Modern BP ammunition is actually a little less powerful than the original because the drawn brass cases used today have thicker walls than the old balloon head cases leaving less room for powder. My .44-40 ammunition is actually .44-35
Son was pretty impressed, thank you all again. He’s done, I’m still reading. So, Clint Eastwood wasn’t really lying at the time, when he said a .44 Magnum was the most powerful handgun in the world? Or was it bravado/crappy Hollywoodism?
I’ve talked to law enforcement people about the argument posed in that first Dirty Harry movie, which says that a .38 special bullet might indeed deflect from a car windshield, whereas a .44 magnum bullet will not. I guess this is due to the greater force behind the bullet itself, the so-called magnum casing?
At the time the movie was made, Harry Callahan’s statement was more or less true, if you limit your consideration to “conventional,” widely-available handguns. There were certainly more powerful handguns then, but they were generally bolt-action, single-shot, very specialized hunting/target pistols. Not the sort of thing Harry would carry.
As far as windshield penetration, the likelihood is as much a function of impact angle as it is “force” or energy. Either bullet will penetrate at a right angle (perpendicular to the glass), but neither will if the angle is sufficiently oblique. However, at any angle, the .44 Mag is more likely to penetrate because it carries roughly four times the energy of a standard .38 Special. (I used standard PMC loads for the comparison, .38 Special, 158 gr., 800 fps muzzle vs. .44 Mag., 240 gr., 1300 fps muzzle, yielding 225 ft.-lbs. vs. 900 ft.-lbs.)
It’s not so much the “magnum casing,” but the fact that it’ll hold a lot more powder. Typical .44 Mag loads use more than twice the powder of a typical .38 Special load. Also, handguns chambered for the .44 Mag. are built to withstand roughly twice the chamber pressure of a .38 Special.
.44 magnum was the most powerful commercial revolver in the world at that time. Other, single shot, handguns like the Thompson-Center Contender were available that were technically more powerful than Dirty Harry’s .44 magnum. Those guns, however, used actual rifle cartridges or wildcat cartridges like the .30 Herret and .357 Herret. A wildcat is a cartridge not used in a production firearm or loaded by a major manufacturer. You produce them yourself at home with reloading equipment. When the .454 Casull, which Dick Casull began developing all the way back in the '50’s, became commercially produced the .44 lost the crown of “most powerful handgun in the world.” There have also been other cartridges as-or-more powerful than the .44 introduced over the years. Some were commercially successful and are still available, others not. The .400 Cor-bon, .50 AE, and various Wildey calibers (for the Wildey pistol) come to mind for starters.
The .44 mag was probably the most powerful factory handgun round available in the early seventies but there are a lot of “ballistic inconsistencies” to say the least.
Bullet type and angle have as much to do with deflection as bullet mass and velocity. Bullets, even from rifles, will easily bounce off water with a flat enough angle. Also the .38 special had been considered old hat since the .357 magnum had come out in the mid thirties. When revolvers were starting to be replaced by “wonder 9” semi-autos I read a statistic that the .357 magnum 125 grain jacketed hollow point had the best record in actual police shootings of any caliber/load combination. Also in one of the movies Harry states that he used light special loads in the magnum revolver to reduce recoil. So much for the “most powerful handgun” B.S.
The Colt Walker probably held the “most powerful” title the longest, from 1847 until the .357 magnum came out in the mid thirties. It could hold up to 60 grains of powder which was really too much for the state of the art in metalurgy back then. There were only 1,100 originals and now many times that many reproductions by at least three manufacturers in Italy. Mine is from Aldo Uberti 
I don’t shoot mine with maximum loads as it beats up and loosens the wedge that holds the barrel on. Recoil is actually quite mild becase of the mass and size. It’s about 4.5lb and over 15". The only risk is getting a sore arm and wrist from holding it up. It’s so big looks like someone’s idea of a joke to use as a comedy prop. It was never intended as a belt pistol but to be carried on a pommel holster on a saddle by the Texas Rangers. Someday I may load a few maximum charges just for grins and measure velocity with a cronograph to see how powerful it really is.