What is a True Magnum Cartridge?

What is a True Magnum Cartridge?

Magnum Cartridge

BY JON R. SUNDRA: When it comes to defining magnum cartridges, it’s not as straightforward as you might think.

There was a time when the term “magnum” was fairly well defined. I’m talking back in the 1960s and 70s when the word pretty much meant a cartridge more powerful than “normal” and was usually based on the belted Holland & Holland case. In fact, in the eyes of many, if it didn’t have a belt, it couldn’t be a magnum—that’s how synonymous the two words became. As always, though, there were many exceptions to the rule. Back in its early days as a wildcat, for example, the .25-06 certainly provided magnum performance if the standard for the caliber was the .257 Roberts. Yet it was never called a magnum.

At the other end of the .25-caliber spectrum was the .256 Win. Mag., a bastard of a cartridge if ever there was one. Originally designed as a pistol cartridge, what limited popularity it achieved was in the Marlin Model 62 Levermatic rifle.

Based on the .357 Mag. pistol case necked down to .25 caliber, as a rifle cartridge it was pitiful, sending a 60-grain bullet of low sectional density and ballistic coefficient at 2,760 fps. If we again cite the .257 Roberts as representing the performance standard for the caliber, it would have qualified as a super magnum compared to the .256. Incidentally, I actually owned one of those Marlin Levermatics, and the .256 Win. Mag. was the cartridge with which I started my handloading career.

Anyway, another and even better example of confusing nomenclature is the .220 Swift. When it was introduced in 1932, it absolutely blew the doors off any other .22 centerfire cartridge, yet like the .25-06, it never received the magnum imprimatur. Even when the .222 Rem. Mag. was introduced in 1958, the Swift pushed the same weight bullets about 500 fps faster, yet it was…well, just a Swift, not a magnum.

Like I said, there are many exceptions to the rule, but for the most part there was some thread of consistency throughout cartridge nomenclature. I guess when you get right down to it, a cartridge is regarded as a “magnum” if its performance—usually based on velocity, but not always, as in the case of shotshells—is higher than the nominal standard. Today we have many true magnums that have no belt, plus we have short magnums, ultra magnums and “enhanced performance” cartridges, so determining what those standards are is a lot more confusing than it used to be.
The .30-06-based .280 Rem. (second from left) represents standard velocity for the 7mm caliber. Like the .30 family, the smaller .308 Win. based 7mm-08 next to it comes close to matching the .280, while the belted 7mm Rem. and 7mm Ultra Mag provide one and two levels of performance above it.

The .30-06-based .280 Rem. (second from left) represents standard velocity for the 7mm caliber. Like the .30 family, the smaller .308 Win. based 7mm-08 next to it comes close to matching the .280, while the belted 7mm Rem. and 7mm Ultra Mag provide one and two levels of performance above it.

I do think, however, we would all agree that the performance “standard” for our two most popular hunting calibers, the 7mm and .30, are represented by the .280 Rem. and the .30-06. In other words, a muzzle velocity of around 2,800-2,850 fps for a 150-grain 7mm bullet, and 2,750 or thereabouts for a 180-grain bullet in a .30-06, represent “standard” cartridge performance for those respective calibers.