This article first appeared at Range365.
Few experienced handgunners question the legitimacy of the .357 Magnum caliber. While it still has the limitations of any handgun cartridge, it has developed a reputation as a fight-stopper since its introduction in a revolver by Smith & Wesson way back in 1935.
The .357 Sig is a cartridge that was designed to allow for near-.357 Magnum ballistics in a semiautomatic pistol. And there’s a lot to know—and like—about the .357 Sig. Here are some of the most interesting facts about this unique cartridge.
It’s a .357 Magnum for Pistols
Projects like cartridge development are always a team effort. In this case, SIG Sauer worked with Federal Premium Ammunition to develop the cartridge for release in 1994. The goal was to provide similar magazine capacity and dimensions of the popular .40 S&W, while replicating the ballistics of the revolver-only .357 Magnum.
And it’s nearly the same. The “classic” loading of a .357 Magnum cartridge has a 125-grain, .357-inch diameter bullet launching at about 1,500 feet per second, give or take, depending on the specific load. The .357 Sig can do almost that, with most factory loads launching a .355-inch, 125-grain bullet between 1,350 and 1,450 feet per second. However, the .357 Magnum can also launch a much heavier bullet, like a 158-grain one, at high velocity. Due to case length limitations, .357 Sig loads only get up to about 150-grains at the high end. But you get the advantages of easier carrying and concealing, improved handing by those with smaller hands, and more ammo capacity with a pistol chambered for the Sig round.
While the lower diameter and case rim dimensions are exactly the same between the .40 S&W and .357 Sig, the Sig round has a bottleneck profile to hold the smaller .355-inch diameter bullet. The case itself is also 0.009 inches longer. The bottleneck-shaped cartridges feed smoothly from magazines into the chamber, so .357 Sig guns have proven themselves to be extremely reliable. (Some folks make their own .357 Sig cartridge cases by reshaping .40 S&W brass. That will work, but isn’t recommended because the cartridge will end up being slightly shorter than its official specification.)
Other notable law-enforcement organizations have used the .357 Sig over the years, including the U.S. Secret Service, Federal Air Marshals, and the Texas Rangers.
Not all Loads are Equal
Some manufacturers choose not to provide the full performance capability of the cartridge. For example, Hornady loads its .357 Sig Critical Defense ammo with a lighter 115-grain bullet traveling at only 1,235 feet per second. Their 135-grain Critical Duty load moves at 1,225 fps. On the other hand, Mike McNett, the godfather of Doubletap Ammunition, loads his 125-grain cartridges to cook along at 1,525 feet per second. If you want to be all you can be when using a .357 Sig pistol, choose your ammunition carefully.
Kinetic energy is one measurement of the “oomph” of any given cartridge. While you can’t make generalizations that one bullet is twice as good as another if the kinetic energy is doubled, you can use the measure as a guideline. Many other factors like momentum, diameter, and bullet design come into play if you’re trying to develop a picture of the overall destructive power of any given caliber and cartridge combination.