357 Sig vs. 357 Magnum

357 Sig vs. 357 Magnum


The .357 Magnum is one of the most popular cartridges in the United States. It has been around for almost ninety years, is extremely well-known, and is the original Magnum chambering. There’s a lot to recommend the .357 Magnum. In the other corner is the .357 Sig, the Millennial of handgun cartridges. It’s young, it’s cool, it has all of the best features of the .357 Magnum. And yet the .357 Sig, acclaim, popularity, and loyal following that the .357 Magnum enjoys, even as it approaches its tenth decade.

Let’s take a look at these two handgun rounds. Both fighting in the same weight class, the .357 Sig and .357 Magnum are really similar…but also completely different. The .357 Sig vs. the .357 Magnum – which is better, which is worse, which one is for you? Let’s start with a little background on each, then put them head-to-head.

.357 Magnum

The .357 Magnum was introduced in 1934, and it was the first cartridge to be designated a “magnum.” A collaborative effort between Winchester and Smith & Wesson, the .357 owes a lot of its lineage to Elmer Keith. Keith (if you don’t know him you’ve got a reading assignment!) was an early hunter, hand gunner, and wildcatter experimenting with loading the .38 Special to increasingly high velocities. This led to the development of the .38-44 HV (“-44” because these guns were built on .44-caliber frames to handle the required pressures), which led to the .357 Magnum.

The .357 Magnum runs at more than twice the pressure of the elderly .38 Special. To prevent the longer magnum cartridges from being loaded in .38 revolvers – either by mistake or out of ignorance – the .357 Magnum was made 1/10th of an inch longer than a .38 Special case. The impetus for all this development was the prevalence of the .38 Special used by law enforcement at the time. Firing lead round-nosed bullets with puny muzzle velocity, these guns had a poor track record of stopping the bad guys of the day, and were no match at all for the auto bodies of that era.

The .38 Super Automatic cartridge from Colt, chambered in the 1911 platform could punch through car doors and the body armor of the era. Police departments wanted something with the muzzle velocity and muzzle energy to punch through cars and provide ample stopping power. The brains behind the .357 Magnum wanted a revolver cartridge that could do the same. Thus began the Magnum era and once widely adopted, .357 Magnum revolvers were almost universal in law enforcement holsters until the 1980s. Civilian shooters immediately recognized the potential of the .357 Magnum, too. Eighty years later is still wildly popular for self-defense.

The Magnum cartridge very quickly gained a reputation as a round that would make quick work of a bad guy. The powerful cartridge launched a 125-grain jacketed hollow point at round 1,400 feet per second. This reputation was bolstered as handgun hunters began taking mid-sized game with .357 revolvers, and was further boosted by 1992’s Handgun Stopping Power by Marshall and Sanow. The book gave the 125-grain Magnum load from a 4-inch barrel a peerless 97% one-shot-stop record. Though we can question the validity of these statistics now, the cat was out of the bag and the .357 Magnum was immortalized.

.357 Sig

Sixty years after the birth of the .357 Magnum, the .357 Sig came along. Born in 1994, the .357 Sig was intended to offer ballistics similar to those of the .357 Magnum, but in a semi-auto handgun. This was post-Miami-Shootout, the FBI was still issuing the 10mm Auto, and the quest for more power and deeper penetration was on every one’s mind. The .357 Sig appeared to offer the best of both worlds – the power of the .357 Magnum and the capacity, ease of operation, and fast, sure reloading of a semi-auto, .40-caliber pistol.

The .357 Magnum has always been problematic to load in semi-automatic handguns for a couple reasons. First, the cartridge is long – 1.59 inches. This makes a semi-auto action long and, resultingly, heavy. The second problematic feature of the .357 Magnum is its rimmed case. This can cause rim-lock if magazines are not loaded correctly. A few oddball semis are chambered in .357 Magnum but they are enormous, heavy, and not known for reliability. In short, they are no good for duty or carry. The .357 Sig, a joint project between gun manufacturer Sig Sauer and ammunition maker Federal, sought to alleviate both of these problems. 

In order to get enough gunpowder in the case to push a 125-grain bullet at Magnum muzzle velocities, the .357 Sig has a bottle-neck (rather than a straight-walled) case. Based on a 10mm case, it fires a 9mm-caliber bullet. The bottleneck design inherently increases pressure, and therefore velocity. It also has the added, theoretical benefit of making the pistol feed more reliably. The smaller bullet can fit easy into the massive chamber opening, preventing feed way stoppages. In reality this isn’t a huge benefit as most duty pistols made these days are incredibly reliable.

The result was a pistol cartridge that packed a wallop. Published ballistics for the .357 Sig show a 125-grain bullet leaving the muzzle at around 1,350 feet per second (f.p.s.). That’s considerably more powerful than the nearest competitor, the 9mm Luger. Unfortunately, it also generates significantly more recoil and is much harder on guns. The .357 Sig was adopted by a few high-profile law enforcement agencies including the Secret Service, the Federal Air Marshal’s Service, and the Texas Rangers. Despite this it never gained the widespread popularity of the .357 Magnum, which was adopted by police departments from border to border and coast to coast.

.357 Sig vs. .357 Magnum

That’s the backstory – now let’s put these two cartridges head-to-head. Which is better: the upstart, .357 Sig cartridge or grandaddy of ’em all, the .357 Magnum? Both of these cartridges offer really similar ballistics. Neither has significantly less recoil, and both have fairly substantial muzzle blast. The .357 Magnum has a slight edge in muzzle velocity, but really it is secondary factors that will determine which of these is better for you. Let’s look at some of these factors. 

Ammunition Availability: the .357 Magnum enjoys a tremendous advantage in ammunition availability. The .357 Sig never gained widespread acceptance, and therefore manufacturers don’t make as much ammo for it. If you find yourself in the hinterlands, out of ammo and needing to resupply the local gun shop, .357 Magnum will be on store shelves, but they might not have .357 Sig. And that brings up another “pro” for the Magnum round…

Ammunition Versatility: A .357 Magnum revolver can fire .38 Special ammo. If you can’t find a box of Magnums, you can load up with .38s. This is also great for plinking, introducing recoil-sensitive shooters to hand gunning, or even taking small game. And it’s great when store shelves are bare – you have to cartridges you can choose to feed your .357 Magnum with: .357 or .38 Special. Since the .357 Magnum is a revolver cartridge, it will also function with light bullets, heavy bullets, and even weird bullets like shotshells. A .357 Magnum revolver will also perform fantastically with ultra-heavy, super-wide flat-nose bullets for protection against dangerous game. You just don’t get that versatility and flexibility with .357 Sig.

On the other hand, the .357 Sig has similar versatility with the addition of a conversion barrel or two. The .357 Sig is such a powerful cartridge, pistols built for it are tough. They are tough enough to handle lighter cartridges like 9mm and .40 S&W. Drop in a conversion barre and now your pistol is a .357 Sig and a 9mm. This is a unique kind of versatility, though it does incur some extra expense.

Form Factor: If you want a revolver, you’re going to have to get a .357 Magnum, and if you want a semi-auto, you’re going to have get a .357 Sig. That’s a pretty clear differentiator, and a place where the Sig cartridge shines. The semi-auto has much higher capacity; the Glock 31 in .357 Sig holds 15+1, a clear advantage over revolvers of comparable size that hold 6+1 or 7+1. Even the subcompact Glock 33 holds 9+1, more than any duty-caliber revolver on the market.

There is also the matter of firearm availability. Sig pistols are widely available in .357 Sig, as are Glocks. Not too many other manufacturers are making a .357 Sig pistol. On the other hand, almost everyone makes a .357 Magnum. There are a huge array of magnum revolvers from the original gun, the Smith & Wesson Model 28 to some truly modern marvels.

Which is Better: 357 Sig or 357 Magnum?

Which is better largely depends on your needs and personal preference. Both will work admirably for personal protection. Both will work great for similarly-sized game. And both are a heck of a lot of fun to shoot. The terminal ballistics of each are very similar.

We admit a bias toward the .357 Magnum cartridge, if you’re looking for something in this weight class. The .357 Magnum has been around forever, ammo is plentiful for it, and it has the versatility of allowing us to shoot lighter, cheaper, quieter .38 Special ammo. It also has the ability to shoot a huge array of bullet weights. Those are pretty big advantages. Throw in the fact that it was designed by Elmer Keith, and, we’ll borrow a passage from Skeeter Skelton here, “…if you cast aspersions on my .357 Magnum six-gun, get somebody to hold your coat. We’ll continue the discussion in the alley.”

On the other hand, if you need hard-hitting cartridge, one ballistically comparable to the .357 Magnum, but need it chambered in a semi-automatic pistol, the .357 Sig is an outstanding option. It boasts outstanding capacity, on par with .40 S&W handguns, and comes in a standard frame size, unlike bigger cartridges like the 10mm Auto. Recoil can be demanding, but the same can be said for its Magnum counterpart, and it’s nothing an experienced hand gunner can’t tame. Like we said, this will largely come down to your needs and personal preferences.

Regardless of which you choose, Grizzly Cartridge has you covered with the hottest ammunition around. Our 125-grain .357 Sig loads leave the muzzle at a blistering 1,500 feet per second. We also manufacture some of the finest, heaviest, hard-cast lead flat noses for your .357 Magnum revolver, as well as some light .38s, and some spicy .38 +Ps.

Grizzly Cartridges are built from the highest quality components to give the ultimate performance, each and every time. Consistent, reliable, and made-in-the-USA, trust Grizzly Cartridge for your handgun ammo, regardless of the purpose, from personal protection to handgun hunting.