.357 Sig is my favorite pistol cartridge. I don’t really know why, I just think it’s cool. Well, seriously speaking, it is a screamer with great street performance and the bottleneck design helps not only velocity, but feeding reliability.
Developed by a pas de deux featuring Sig Sauer and Federal Ammunition in 1994, it’s loosely based on a necked down .40 S&W cartridge – conceptually anyway. The idea of .357 Sig is to launch a .355 caliber bullet form an autoloading pistol a few hundred feet per second faster than a 9mm cartridge can.
With that said, consider these interesting facts about the .357 Sig…
It’s like a .357 Magnum, but not really.
You’ll hear descriptions of the caliber like “it offers .357 Magnum capability in an autoloader that’s not a Coonan.” That’s partially true, if you’re talking about a .357 Magnum firing a 125 grain bullet. DoubleTap Ammunition markets 125 grain .357 Sig loads that clock 1,525 feet per second from a 4 ½ inch barrel. That’s about 645 foot-pounds of muzzle energy, and within .357 Magnum territory for a 125 grain projectile. The ‘not really’ part comes into play when you consider 158 grain .357 Magnum loads. DoubleTap also produces a 158 grain .357 Magnum load that achieves 1,540 feet per second from a 6-inch barrel revolver. That’s about 832 foot-pounds.
It’s like a 9mm on steroids, but not really.
The .357 Sig uses a .355 inch diameter bullet like the 9mm, not a .357 diameter bullet like the .357 Magnum and .38 Special. While the bullet diameter is the same as the wonder nine, most .357 Sig projectiles are shaped differently. To take maximum advantage of the limited case neck real estate in the bottleneck portion of the cartridge case, many .357 Sig projectiles do not have elongated noses like 9mm designs. The bullet body, or bearing surface, will be long enough so that when seated to the proper depth, every bit of the case neck will be in contact with the projectile. Remembering that the overall cartridge length still needs to remain in spec, this means the nose will generally have more of a blunt profile.
Some 9mm bullets will work and some won’t. If you reload, be careful about this as bullets with the wrong profile are susceptible to pushing back into the case during feeding or recoil, thereby generating dangerous pressure levels.
It’s based on the .40 S&W, but not really.
The internet says you can make brass from .40 S&W brass. I’m also sure you can find someone on the internet with instructions to convert a 1970 Gremlin into a gas-powered vegetable juicer. Just because you can doesn’t mean it’s a good idea.
For starters, the .40 S&W cartridge case length is normally .850 inches while the .357 Sig is not only bottlenecked, but measures .865 inches. Sizing a .40 S&W case to create a .357 Sig bottleneck may stretch it a bit, but generally not enough. More importantly, there are other case differences, like pressure. We’ll talk about that next.
Finding a productive use for a Dremel tool around guns, I cut some .357 Sig and .40 S&W cases in half. Recognizing that there are differences from manufacturer to manufacturer, and dimensions will always vary a bit, I did find that the case walls were thicker on the Sig cartridges. Measuring about half way up the case, the .40 S&W brass was about .010 inches while the .357 Sig brass was about .015 inches at the same point. I know, not scientific, but I was curious and wanted to use my Dremel powers for good.
The .357 Sig feels the pressure.
According to the Sporting Arms and Ammunition Manufacturer’s Institute (SAAMI), the average pressure for the .40 S&W is 35,000 psi. The .357 Sig has an average pressure of 40,000 psi. That extra 5,000 psi is a lot of mojo to be fooling around with. To put that in perspective, a scuba tank usually holds between 2,900 and 4,400 psi and you saw what one of those did to Jaws, right? The moral of the story is while it’s technically possible to make something resembling .357 Sig brass from a .40 S&W case, don’t do it.
The .357 Sig head spaces on the case mouth, or maybe the case shoulder.
Here’s a bit of minutia sure to start a reloading room fight.
By the way, if you don’t know what the process of “head spacing” is, think of it as as the relationship between the part of a cartridge that jams into a part of the chamber to set the exact distance between the bottom of the case and the breech face. In other words, all of this makes sure that the firing pin is the correct distance from the cartridge and that the cartridge fits in the closed chamber without moving back and forth more than it’s supposed to.
In a straight wall semi-automatic cartridge like the 9mm, the edge of the cartridge mouth catches on a ledge in the barrel chamber to set head space. In many rifle cartridges, the shoulder of the cartridge pushes into the shoulder of the chamber to set head space. With the .357 Sig, according to a 2007 ruling of the C.I.P. governing body, that would be Commission Internationale Permanente Pour L’Epreuve Des Armes A Feu Portatives for those of you who can read the menus at French restaurants, the cartridge head spaces on the shoulder. Of course, that’s all hypothetical. Where your .357 Sig pistol actually head spaces depends on your ammo and the chamber of your gun.
The .357 Sig can create black holes.
Through rigorous scientific process, advanced instrumentation and a large glass jar of grape jelly, I was able to prove that one can create a short-lived Welch’s Black Jelly Hole by shooting said jar with a .357 Sig 125 grain Speer Gold Dot projectile. While I did not have any gravitational lens or emitted radiation detection equipment handy, I think creation of a black hole is the only rational explanation for the complete disappearance of all grape jelly traces. I still have no explanation for the unwarranted anger of other shooters at the range who were mysteriously coated with a purple sticky substance.
Highway Patrols and the Secret Service love the .357 Sig
Reports from law enforcement use indicate that the .357 Sig caliber is exceptionally effective at stopping evil dudes from doing evil things. For some reason, law enforcement popularity seems to be limited to federal agencies and state highway patrol forces. The United States Secret Service uses the .357 Sig as do Federal Air Marshals. On the state side, if you include state police and highway patrol organizations, you’ll find .357 Sig cartridges in use in North Carolina, Texas, Mississippi, Delaware, Montana, Rhode Island, Virginia, Tennessee and New Mexico. You might also be interested to know that the Orlando Police Department relies on .357 Sig to protect the perimeter of one of our most important national assets – Mr. Toad’s Wild Ride at Disney World.
I’m not going to get into issues of whether the .357 Sig is “more betterer” than other cartridges – that’s always an argument with no possible clear outcome. It’s different, unusual, and apparently pretty darn effective on the street. That’s good enough for me.
For a comprehensive look at a variety of .357 SIG rounds extensively chronographed, check out the results from Ballistics By the Inch. They do rigorous, independent testing, and provide easy to read charts.