The word "magnum" is Latin, and it simply means big. A man's "magnum opus" is his life's major work, like Tolstoy's War and Peace. It's also applied to oversized bottles of champagne.
Sometime after 1900, someone used it to describe a cartridge that was more powerful than a predecessor- that is, relatively big- and we progressed from there. Over the last century, the term has drifted in and out of favor. At one point, any cartridge with a belt was called a magnum; some cartridges that carried the term did not deserve it, while others that did deserve it, did not. It's safe to say, as dawn brightens the sky of this spring of 2018, the term has become largely meaningless.
One cartridge that richly deserved the name is the .44 Magnum- simply the .44 Special lengthened to deliver more power. By that yardstick, another genuine article is the .32 H&R Magnum.
The .32 H&R
This cartridge has probably been ridiculed for its name more than any other except, perhaps, the obscure .256 Winchester Magnum, but speaking as a purist, I think it deserves the name more than most. This is because it is the venerable .32 S&W Long lengthened by 0.15 inch- exactly like the .44 Mag. and .357 Magnum. And like those two, it offers the significant advantage of allowing the use of light target loads of the parent cartridge or hefty magnum loads from the same gun.
If you have never spent time with the .32 S&W, you are missing a good thing. In the right gun, it's one of the most accurate handgun cartridges ever developed. Alas, so many ramshackle old .32 revolvers are floating around that it's gained a reputation as a pimp's gun and nothing more.
This is unjust. One of the nicest-shooting guns I ever owned was a .32 S&W Long Britarm semiautomatic made for Olympic rapid-fire competition. It would accommodate only wadcutter ammunition; anything with the bullet protruding from the case would not fit the magazine. But was it accurate! Sellier & Bellot used to offer match ammunition, and it was lovely. The high-quality cases were also excellent for reloading.
I got into .32s by accident when I fell in love with an S&W Model 16-4, a target revolver made briefly in the early 1990s for the .32 H&R/.32 S&W Long combination. It has a 6.0-inch barrel with a full underlug, cocobolo grips, and a bluing job to make your eyes sparkle. And, yes, I know it's a collector's item, and yes, I shoot it anyway.
Not many gunmakers picked up the .32 H&R, and those that did sometimes adapted .38 Special frames. For example, Ruger made a Blackhawk that was actually heavier than the same gun in .357 Mag. because barrel and cylinder were the same but the bore and chambers were smaller. Instead of getting a lighter, handier gun, you got a heavier one. (I realize Ruger also chambered the .32 H&R in its lighter and smaller Single-Six SA revolver, as well as the small-frame double-action SP101 and recent polymer-frame double-action LCR revolver.)
In addition, for a long time, the only source of either loaded .32 H&R ammunition or brass was Federal. The selection was limited to two bullets (85-grain jacketed and 95-grain cast), and it was, to put it politely, anemic. If you wanted to get any real action out of your .32 H&R, you had to handload. Fortunately, enough good bullets were around, originally intended for the .32-20, that you could cobble up some good small-game and plinking loads. Today, there is more variety in bullets, including the Hornady 85-grain XTP, the Sierra 90-grain JHC, and the Shooter's Choice 100-grain cast bullet.
In 2008 Federal and Ruger teamed up to create the .327 Federal Magnum, which lengthened the .32 H&R even further. That cartridge is a whole separate subject, but because it will shoot the .32 S&W Long as well as the .32 H&R, it encouraged the production of more bullets in .32 caliber. For this, my Smith & Wesson Model 16-4 and I are truly grateful.