That Darned .357 Sig People Keep Talking About
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 this cartridge, almost like the recurrence of a chronic disease, and some people get curious. There are some good reasons, which we'll get into, but there's also some drawbacks worth keeping in mind as well.
So, without further ado, let's get into the 5 Ws of 357 Sig.
What Is 357 Sig, Anyway?
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, when either was fired from a 4-inch barrel.
Initially, it was then offered in a number of Sig Sauer service pistols such as the Sig P226 and so on.
How did they do it? Basically by necking down and cutting back a 10mm case, so that it held more powder yet still seated a .355-inch (that's 9mm, folks) bullet. It wasn't even the first time that was done, either; the IPSC wildcat 9x25mm Dillon was the same darn thing, but obviously 9x25mm didn't go anywhere.
It's a misconception that it's a .40 S&W necked down to 9mm. Case length of .357 Sig is 21.97mm, compared to .40 S&W which has a case length of 21.6mm. The .357 Sig case also has a tiny bit more capacity (19.6 grains vs 19.3 grains) but not so much that it's worth dwelling on.
357 Sig Ballistics
357 Sig offers some impressive ballistics, but does come with some costs. In fact, this has been the selling point for the round...basically since its inception.
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. That is indeed about the same as that of a .357 Magnum revolver with a 4-inch barrel.
The upshot, then, is a much more powerful 9mm round, meaning that you can get essentially magnum power from a cartridge that can be used in a 9mm pistol frame, which is not the case with the aforementioned 9x25mm Dillon (requires a large frame) 10mm, .400 Corbon or .45 Super, and other hot boutique handgun calibers.
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.
Have a look at Lucky Gunner Labs tests and see for yourself. They use a gel protocol similar to the FBI protocol. What their results suggest is a marginal increase at best in penetration and expansion, though with a significant gain in velocity...when the .357 Sig actually outperforms the 9mm.
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. Speer Gold Dot (124-gr in 9mm, 125-gr in .357 Sig) shockingly yielded an almost 5-inch advantage to the 9mm (13.2 inches to 18.1 inches) but the .357 Sig expanded to an average of 0.67 inches vs 0.54 inches for the 9mm load. Federal HST performed basically the same.
Point being that some testing has revealed that an across-the-board improvement in penetration and expansion is not necessarily the case.
Some contend that .357 Sig travels fast enough to produce hydrostatic shock. This seems unlikely, as few handgun rounds produce the velocity or energy required for that effect to happen in tissue; hydrostatic shock typically requires closer to (if not more than) 2,000 fps of velocity and 1,000 ft-lbs+ of energy. However, this is mere hypothesis; it has never been confirmed that .357 Sig produces any.
What is definitely known is that it has proven itself effective in self-defense capacities. A number of police departments adopted the round as well as some adoption by the US Secret Service and Federal Air Marshals. So is it effective? Yes. Is it the DEATH RAY THAT PEOPLE SAY?! That's a bit of a stretch.
A Note On .357 Sig And Handgun Ballistics
Be very careful drinking the Tactical KoolAid of .357 Sig, 5.7x28mm or indeed any handgun round.
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.
Where .357 Sig will give you an edge - a bit better penetration - is shooting through barriers. Dry wall, doors, auto glass, thin sheet metal and so on. High-velocity bullets excel at barrier penetration. Police officers also found .357 Sig to be very effective at putting down attacking dogs, so it also has some potential as a woods cartridge so long as you don't have to worry about grizzly bears and to a greater degree than 9mm will.
Granted, a long gun makes a better bear gun, as would a .44 Magnum.
Drawbacks To .357 Sig
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.
First is the wear and tear on your pistol. Chamber pressure of .357 Sig is between 40,000 and 44,000 psi, which is rather stout when compared to .40 S&W (around 35,000 psi) and 9mm, which generates about 33,000 psi. More pressure means more wear on the barrel, the frame, and the more violent cycling will accelerate wear on the slide.
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. Few are made for this chambering anymore, and only a few compact pistols at that. Sig Sauer makes only a few, and Glock actually makes more guns in .357 Sig at this point than Sig Sauer does.
Don't even bother asking for the P365 in .357 Sig. They won't, and we know because we asked Sig Sauer directly. They said "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.
Don't get it wrong, though. .357 Sig is a great round, and if you wanted more power than 9mm, but without having to carry a larger-frame pistol like is necessary with 10mm or a revolver as is the case with .357 Magnum, it's definitely a great choice. The question of course is whether it's really worth it in the end.
That much...well, that's up to you.