A super magnum is a longer and/or more powerful version of a "magnum" cartridge. Although the term "super magnum" typically refers to a handgun cartridge, created by lengthening an existing straight-case design, it can also refer to rifle and shotgun cartridges, such as the .17 Winchester Super Magnum and the 31⁄2" 12 Gauge Super Magnum. In this case, it simply denotes that it is of greater power than existing "magnums" of a similar caliber or gauge, this is comparable to other designations, such as the "Remington Ultra Magnum". The most widespread of these cartridges are the "SuperMag" family of super-magnum handgun cartridges that were proposed and tested by Elgin Gates in the 1970s.

Gates tested super magnum cartridges in 7mm, .357, .375, .41, .44, .45, .50, and .60 caliber. His SuperMag cartridges are all 1.610 inches long—about 3⁄10 of an inch longer than a "standard" handgun magnum (i.e. .357 Magnum, .41 Magnum, and .44 Magnum, which are all the same length)—and use the same bullets as the original magnum cartridges. The extra powder capacity can increase muzzle velocity up to 30–40% over the original magnum rounds.

In the 1980s, Dan Wesson Firearms began to produce revolvers chambered for the .357 Supermag, .375 Supermag, and .445 SuperMag cartridges. In 2000, they added .414 Supermag, and .460 Rowland.^[1]

Other cartridges that were created by extending the length of existing magnum cartridges include:

• The .327 Federal Magnum, based on the .32 H&R Magnum.
• The .357 Remington Maximum, based on the .357 Magnum, virtually identical in all dimensions to the .357 SuperMag, but with a slightly shorter overall case length.
• The .460 S&W Magnum, based on the .454 Casull. The latter cartridge is effectively, though not in name, a magnum version of the .45 Colt.
• The .500 Bushwhacker, a lengthened and far more powerful version of the .500 S&W Magnum. The latter cartridge is a magnum of the .500 S&W Special.

Based on the .357 Magnum cartridge, a revolver or single-shot pistol designed for the .357 SuperMag can also fire .357 Remington Maximum, .360 Dan Wesson, .357 Magnum, .38 Special, .38 Long Colt, and .38 Short Colt cartridges. The .357 SuperMag is essentially the same cartridge as the later-named .357 Remington Maximum that was jointly developed circa 1982–1983 by Sturm, Ruger & Company and Remington; the .357 Remington Maximum brass is only 0.005" shorter than the .357 SuperMag brass, but identical in all other dimensions. Ruger, as well as Dan Wesson, introduced revolvers for this cartridge, followed shortly later by Thompson/Center in their single-shot Contender.^[1]Due to flame cutting of the top strap of revolvers when shooting cartridges loaded with 110 and 125 grain bullets, Ruger discontinued their revolver in this cartridge after a short production run. Dan Wesson provided a second barrel to customers, but this failed to address customer fears, and the cartridge remained popular only in the single-shot T/C Contender. Remington then dropped this cartridge from production, although brass is still manufactured for reloaders every few years.

Based on the .375 Winchester rifle cartridge, this custom round was meant to fit between the .357 SuperMag and the .445 SuperMag, but is no longer produced. It had a tapered case that was prone to sticking in the cylinder after firing. The .375 Super Mag took a special jacketed revolver bullet of 220 grains made by Hornady and chambered in the Dan Wesson revolver. But shooters concluded the combination did not shoot very well, and it was dropped from production with few being made. Star-Line brass is likewise rare.

Based on the .41 Magnum cartridge, the .414 SuperMag never really caught on, partly due to medium-range performance not that different to the well-established .44 Magnum. Consequently the cartridge was never adopted by any of the major commercial ammunition producers, although custom ammunition producers listed it, loaded with Starline brass. Dan Wesson did commence chambering their 8"-barrelled, heavy frame revolver for it in 2000; numbers were small due to lack of demand, and production was terminated by their Chapter 11 bankruptcy. They also offered 'factory' .414 Super Mag ammunition, based upon Starline cases topped with a 220-grain TC bullet, now highly collectable. Thompson Center were the only other manufacturer to catalogue the calibre, offering various lengths of chambered barrel for their single-shot T/C Contender. A revolver designed for the .414 SuperMag can also fire the shorter .41 Magnum and .41 Special cartridges. ^[1]

Based on the .44 Magnum cartridge, the .445 SuperMag is a high pressure cartridge and will allow higher muzzle velocities than most .44 Magnum cartridges. .445 cartridges are designed for long range hunting and target revolvers, capable of knock-down performance surpassing 200 yards for Silhouette and 150 yards for hunting applications. The .445 Super Magnum can drive a heavy 300-grain bullet 120 ft/sec faster than the .44 Magnum cartridge. While Dan Wesson handguns in .445 SuperMag ceased production in 2007, custom ammunition producers such as Buffalo Bore continue to offer loaded ammunition. Starline brass is still available and custom manufacturers occasionally offer T/C Encore barrels. A revolver designed for the .445 SuperMag can also fire the shorter .44 Magnum, .44 Special, and .44 Russian cartridges.^[1]

• Taffin, John. The SuperMags SixGuns.com
• Taffin, John. Taffin Tests: The .445 SuperMag SixGuns.com