All About The .357 SIG

A Round That Delivers .357 Magnum Performance With Less Recoil Than A 10mm 

The .357 SIG is what can easily be considered an unusual cartridge in the pantheon of mainstream handgun ammunition. Its popularity peaked a few years ago and has steadily leveled off, but it has its fans in the semi-auto world, and in the law enforcement world, though their numbers may be dwindling. 

The goal of the folks who created the .357 SIG, of course, was to create a semi-auto rimless cartridge that delivered a level of performance equal to the beloved 125-grain .357 Magnum revolver cartridge — another law enforcement favorite. 

A secondary goal was to create a cartridge that delivered felt recoil that was somewhere between that of a .40 S&W and 10mm, but easier to manage than both. 

By those metrics, the .357 SIG was a wild success. Let’s take a look at how this round came to be, and how it fits into the handgun ammo world. 

.357 SIG Cartridge Design 

The .357 SIG is a bottlenecked rimless centerfire handgun cartridge that was originally developed by, as you may have guessed, SIG Sauer, a Swiss-German company, in 1994. While SIG has its own ammo brand now, at the time, it was working with Federal Ammunition to develop the new cartridge.  

It is based on a necked-down 10mm Auto casing, but using a small pistol primer like the 9mm and .40 S&W instead of the large pistol primer used by the 10mm. This fact alone makes the .357 SIG a rarity. It was the first factory bottlenecked handgun round that was commercially available since the long discontinued .256 Winchester Magnum was released in 1961, which was a necked-down .357 Magnum with a .257-caliber bullet.  

The necked-down cartridge would produce higher muzzle velocities, giving the projectile a flatter overall trajectory than typical handgun bullets. This would result in increased accuracy while maintaining the terminal effect on the target. 

To coincide with the release of the new cartridge, SIG released the P229 pistol in 1994 — the first production pistol chambered for .357 SIG and designed with the round’s high chamber pressure in mind. It made a lot of sense, since the P220 line was its most popular at the time, and the P226 9mm was big with law enforcement. 

What It Got Right

The ballistic goals of the .357 SIG were certainly accomplished — the round did what it was supposed to do, deliver .357 Magnum performance from a semi-auto handgun with less recoil than a 10mm. 

Also, not long after the .357 SIG hit the scene, the popularity of the .40 S&W began to take off. While they were competitors, the SIG cartridge benefited from this because gun owners can convert most .40 S&W handguns to .357 SIG by simply swapping out the barrel, and usually the recoil spring, too.

The dimensions are nearly identical and most .40 S&W magazines are the same size as .357 SIG mags. For a while, .357 SIG barrel kits were way more popular than pistols chambered for the round. And, as you can imagine, many gunmakers began offering their .40 S&W models with a .357 SIG option, since they didn’t have to do any more than swap out the barrel and recoil spring, too. 

What the .357 SIG Got Wrong

That all sounds great, so why isn’t the .357 SIG the modern go-to cartridge for law enforcement and self-defense in the 21st century; why is it still the 9mm Luger? 

One of the main factors that kept the public from buying more guns chambered for the round has been the price of the ammo they eat. Almost all .357 SIG factory ammo has been pricey ever since it was introduced. It’s common to find it at nearly double the price of more common rounds like 9mm, .40 S&W, and .45 ACP.

As you might expect, ammo companies also don’t produce a heck of a lot of it every year, which means it’s expensive when you can find it. Ammo manufacturers are busy running their lines and using components to produce more popular pistol cartridges in volume. 

It’s also not very friendly for reloaders. The cartridge has a reputation for being difficult to manage in a reloading press because of the relatively weak shoulder, which tends to collapse when seating a bullet in brass that has been fired more than once, or so people say. Now, on the flip side of that, some of the saltier reloaders will tell you the only people who have trouble reloading .357 SIG are the ones who don’t know what they’re doing. Those same people will then proceed to talk your ear off for an hour and a half about the special annealing process they’ve developed over the past 30 years.  

Regardless, that’s the reputation it got: expensive, hard to find, and hard to reload. 

Plus, compared to the array of 9mm handguns on the market, the options for .357 SIG pistols have never been very broad. So, gun buyers inevitably ask themselves, “If I can’t afford to shoot it enough to make it my daily carry, or even a nightstand gun, is getting a .357 SIG as a safe queen and occasional range toy worth it?” 

Then they start shopping for a 10mm. 

Police departments began thinking the same way, except they started shopping for 9mm pistols. Even the departments that adopted the .357 SIG gradually began to move away from it, mostly because of availability issues. While barrel swap kits were popular for a time when the .40 S&W’s popularity waned and then plummeted, that particular caveat of the .357 SIG vanished along with it. 

What’s Next?

Is the .357 SIG a superior round to its competitors? Probably. Its ballistics are solid, it’s basically a pleasure to shoot in a full-size handgun, and it’s easy to shoot well. Plus, the bottleneck design means feeding issues are exceedingly rare. 

However, is it superior enough to justify the extra cost? Most shooters have said no, but the .357 SIG isn’t dead by any means. It has plenty of fans and it has become something of a boutique factory round if that can be considered a thing at all. Discerning handgunners who get sweaty just thinking about an evening alone with a pile of ballistic charts, crunching data from their last five range sessions from this week, they go for the .357 SIG. And people who already have seven 9mm pistols, three 10mms, and probably a .40 S&W just to have it — they also go for a .357 SIG before they start buying wheelguns or Gucci Glocks. 

That said, if the round has you curious and you have the opportunity to shoot it and you shoot it well, then by all means, go for the extremely well-designed, purpose-driven .357 SIG. There are enough options on the market that you won’t have to settle for a gun or for ammo, most of the time.