357 Sig

Everything You Need To Know About .357 Sig

If you're waiting for .357 Sig to make a comeback...I wouldn't hold my breath. However, if you're curious about it, let's learn what there is to know about the round.

There are intermittent flare-ups of interest in it, almost like the recurrence of a chronic disease, and folks get curious. There are some good reasons, which we'll get into, but the reality is there are more drawbacks than benefits to it. 

So, without further ado, let's get into the 5 Ws of 357 Sig.

What Is 357 Sig?

357 sig pistols

357 Sig is a proprietary cartridge developed by Sig Sauer, the ginormous gun company. The round was developed with one goal in mind:

Push a 125-grain 9mm projectile to the same velocity - or so close that it makes no difference - as a 125-grain .357 Magnum projectile fired from a 4-inch barrel, roughly 1,450 feet per second. 

Velocity of .357 Mag vs. .357 Sig was identical (or at least so close that it didn't matter) in the original 125-grain Federal loading so they more or less accomplished the goal. 

The first .357 Sig pistols emerged soon after, being offered in their (then) core pistol models like the Sig P226, P229, P228 and so on. 

The cartridge itself was developed in conjunction with Federal, who created it by cutting a 10mm case back and necking it down to seat a 9mm (0.355 inches) projectile.

As a result, .357 Sig pistols could be (and are) built on a 9mm pistol frame. 

It is not, contrary to popular belief, a necked-down .40 S&W; OAL of .357 Sig (1.14 in) is about 0.009 inches longer than .40 S&W. As a result, it has a teeny bit more case capacity (19.6 grains vs 19.3 grains) but not so much that it really matters. 

357 Sig Ballistics

357 sig ballistics

357 Sig offers some impressive ballistics but comes with some costs. Specifically, it's harder on guns, harder on the shooter, and more expensive. That isn't new information; this would be a clue as to why it isn't the most popular cartridge in the world for law enforcement or other purposes. 

But what does it do well? 

A 125-gr .357 Sig achieves muzzle velocity in the neighborhood of 1400 to 1475 feet per second, and muzzle energy in the neighborhood of 580 to 620 ft-lbs of energy with most standard pressure loads and a 4-inch barrel, roughly equal to a 125-grain .357 Magnum load fired from a 4-inch barrel. 

Unlike other autoloading .38 caliber cartridges (such as .38 Super, 9x23mm Winchester and 9x25mm Dillon) it's sized for use in a pistol frame designed for 9mm.

When loaded with expanding projectiles, .357 Sig gets (the story goes) the best out of 9mm projectiles. Since hollow point performance is velocity-based (below expansion threshold, nothing happens, above it and the bullet goes to pieces) expansion with quality hollow points is reliable and dramatic. The notion is that a 9mm projectile will penetrate more deeply and expand wider and more reliably from a .357 Sig than a 9mm...

...in theory.

.357 Sig vs. 9mm Terminal Ballistics

357 sig vs 9mm terminal ballistics

None of the respected sources of ballistic testing such as the former International Wound Ballistics Association, experts such as Dr. Marvin Fackler or Dr. Gary K. Roberts, found .357 Sig to be any "better" than 9mm. 

Lucky Gunner Labs tests found only a marginal increase in penetration and expansion compared to 9mm. 

Lucky Gunner uses a gel testing protocol similar to the FBI's ammunition test which puts the bullet through 4 layers of denim into a gel block. 

Their testing found 135-gr Hornady Critical Duty had equal penetration and a 0.04-inch increase in expansion for .357 Sig compared to 9mm. The 124-grain 9mm Gold Dot load outpeformed the 125-grain .357 Sig load dramatically, with 18.1 inches penetration (compared to 13.2 inches for .357 Sig) but the .357 Sig loading expanded to 0.67 inches on average vs 0.54 inches in the 9mm load. Federal's 124- and 125-grain HST loads were near as makes no difference identical. 

In other words, what testing is available indicates there's no real advantage. 

Some contend that .357 Sig exhibits hydrostatic shock, which is totally and patently false. No handgun load propels the bullet fast enough (with enough kinetic energy) to actually produce hydrostatic shock; it doesn't happen with any projectile traveling slower than 2,000 fps with 1000+ ft-lbs of energy at minimum. Even the much-ballyhooed 5.7mm doesn't produce hydrostatic shock; it only occurs with rifle cartridges, has always only occurred with rifle cartridges and never, ever, will be a thing with a pistol bullet. 

Nothing emerged in terms of any department that issued it finding any cause for dissatisfaction, including the US Secret Service and Federal Air Marshals, and some metropolitan agencies found it was very effective against aggressive dogs. 

So is it effective? Yes. Is it the DEATH RAY THAT PEOPLE SAY?! No. It's just a hot 9mm. 

.357 Sig Ballistics In Greater Context

357 sig handgun

Be very careful drinking the Tactical KoolAid of .357 Sig, 5.7x28mm or indeed any handgun round. A lot of people believe fantastical things about what pistol bullets actually do, and the reality is that pistols only poke holes in things. Pistols, as Tom Givens says, are basically cordless drills. 

What has been established over the years is that absent ammunition failures and failures of marksmanship, most handgun rounds are near as makes no difference equally effective when placed properly. In other words, it makes little difference if you carry a 9mm, a .357 Sig, .44 Magnum or a .45 ACP. If you've chosen a good personal protection round, and carry quality ammunition, and if you put it where it needs to go in a person that is threatening your life, it will do what needs to be done.

Placement and penetration are the lion's share of lethality. 

As mentioned, it was found to be very effective on aggressive dogs so it may have some potential as a woods round so long as you don't have to worry about brown bears. Granted, it should go without saying that a rifle or a shotgun is always a better bear gun

Aside from that, there has never been - to date - any published evidence (not anecdotes or conjecture; evidence) that .357 Sig does anything better than 9mm, except for putting wear and tear on police pistols and costing more. 

What's The Best .357 Sig Pistol? Can You Get A Sig Sauer .357 Sig Anymore? 

best .357 sig pistol

.357 Sig is dying and/or dead. The only major gun company still making pistols in this chambering is Glock.

Therefore, the two best pistols of current production are the Glock 31 and the Glock 32. These are the .357 Sig equivalent of the Glock 17 and Glock 19, respectively.

There is also the Glock 33, a subcompact (a Glock 26 in .357) if you like suffering. 

Sig Sauer does offer Caliber X-Change kits for P320 Compact and P320 Carry pistols. You just have to swap in your current Fire Control Unit from your existing P320 pistol.

Aside from the Glock .357 Sig pistols, you'll have to dip into the used market. There's no definitive "best" among them, but there are some very good choices.

The original Sig Sauer .357 Sig pistols make a good case for themselves, especially the Sig P226 and P229. The Sig P228 and P239 are out there as well. They are reliable and can handle the .357 Sig round with ease.

There are a small number of .357 Sig 1911 pistols out there, mostly Sig Sauer 1911 pistols. Smith & Wesson had a brief run of M&P357 pistols, and H&K likewise made USP Compact and P2000 pistols chambered in .357 Sig though in small numbers.

If one had to select from the used market, the P229, P226, and USP Compact would be the best. The S&W M&P357 would also be a decent choice, as the M&P series was designed for the ground up for .40 S&W rather than 9mm.  

357 Sig Drawbacks And Pitfalls

sig sauer 357

There are a few known drawbacks of .357 Sig, and if you're curious about the cartridge, these are the pitfalls that you need to know about.

Internal .357 Sig ballistics are more violent than .40 S&W and 9mm.

Chamber pressure of .357 Sig ammo is typically 40,000 to 44,000 psi, more than 10,000 psi more than 9mm (typically 33,000 psi) and .40 S&W, which is typically around 35,000 psi.

The additional slide velocity and chamber pressure put mroe wear and tear on the gun, meaning even the best .357 Sig pistol is going to take a beating. .40 S&W pistols are already known for shorter life cycles, as are 10mm pistols (for those same reasons) and it's a contributing factor in why so few agencies adopted and kept issuing .357 Sig pistols. 

Granted, few gun owners shoot enough to wear out any gun so perhaps that isn't the greatest concern, but is a known quantity.

Sheer cost is another factor. Typically, .357 Sig ammunition is about double the cost of 9mm ammunition if not more, and is rarely found on store shelves. You can shop online, of course, but even then selection is still not as good as 9mm, .40 or .45.

Available pistols is another consideration. Glock is the only company still making them; Sig Sauer has dropped it entirely...and they invented the cartridge. That's what we call "a clue."

Don't even bother asking about a P365 in .357 Sig. They won't, and we know this for a fact because Phil Strader (Sig Sauer's product manager for firearms) told us point-blank at SHOT Show 2019 that "we'd make one in .45 ACP before .357 Sig, and we aren't ever going to make one in .45 ACP."

Then there's the recoil. A .357 Sig pistol that weighs about 2 lbs, firing the classic 125-grain load, will generate something like 9 ft-lbs of recoil, roughly double that of 9mm though slightly less than the recoil of a .40 S&W pistol of that same size and weight firing the classic 165-grain and 180-grain loadings.

Is it a bad cartridge? Not at all. It's a hot 9x19mm, and 9x19mm is the global standard for good reason. It's just that it doesn't do anything so much better than anything else that it's proven itself to be worth it to most police departments and to most people.  

But, it does have its fans, and that's fine.