reloding ,balistic,ammo The .357 SIG

Duplicating the ballistics of a revolver classic, this bottlenecked number is a first-rate defense load for auto aficionados.

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The .357 SIG is a true 9mm, designed to replicate the ballistics of the .357 Magnum’s 125-grain loading from a four-inch revolver, in an auto. From left to right 9mm Luger, .357 SIG, .40 S&W, .357 Magnum.

Almost any 9mm (.355 inch) bullet will work fine in the .357 SIG. From left to right Sierra 115-grain FMJ, Sierra 125-grain JHP, Hornady 124-grain XTP, Speer 147-grain GDHP.

the .357 SIG was jointly developed in 1994 by SIG Arms and Federal Cartridge with one purpose in mind to provide the ballistics of a 125-grain JHP out of a .357 Magnum revolver, but from an auto.

At first glance this would seem improbable, but consider that the .357 revolvers carried by most police officers and armed citizens have (at most) four-inch barrels. Viewed in this context, the .357 SIG achieves its goal quite admirably. Numerous .357 SIG factory and handloads regularly produce velocities in excess of 1,350 fps, and many law enforcement agencies around the nation issue pistols chambered for it. The .357 SIG is a versatile cartridge in every respect that can fill a duty or personal-defense role, as well as provide loads of practical plinking fun.

The design is essentially a necked-down .40 S&W, but reloaders should not try to make cases out of the larger round. Cases so made will wind up about .02 inch too short, and the .357 SIG headspaces on the case mouth, just like most other auto cartridges, not on the shoulder of the bottlenecked case, as one might expect. Besides, there are a multitude of new and fired cases available for reloading. I used once-fired Starline brass for my test loads. Another big advantage of the .357 SIG is that it slithers into the chamber so easily. In fact, my .357 SIG pistols will chamber a fired case from the magazine every time.

Handloading is a snap. Yes, the cases have to be lubricated, but this is no problem. Just lay out a big batch of cleaned cases on a towel and give them a very light shot of Hornady One Shot Lube Spray or Midway Minute Lube. Roll them over with the palm of your hand, and give them another light shot of lube. Let the cases dry, and you’re ready to load. If you feel especially industrious, you can wipe off the lube, but I seldom do and everything functions to perfection.

The modest case capacity calls for standard primers. I used Winchester WSP primers for all loads. Medium-burning-rate pistol powders such as AA-7, Longshot, Blue Dot and Vihtavuori N-350 are good overall choices, and a wide variety of jacketed bullets from 90 to 147 grains of various constructions are available.

Our test gun was the superb Springfield Armory XD-357. Its 3.9-inch barrel has digested many thousands of handloads without a whimper or malfunction. (Virtually all loads grouped into two inches, some considerably less.)

I used a set of Redding dies to prepare all loads. This is a three-die set. The expander imparts a slight bell to ease bullet seating, and the seater die applies a nice, firm taper crimp to the case neck. And, of course, the shellholder for the .40 S&S is the correct one for the .357 SIG, too. (Useful trivia: This shellholder is also correct for the .224 Weatherby Magnum.)

Despite the “.357” in its name, the SIG cartridge is a true 9mm and uses .355-inch jacketed bullets. Some 9mm JHPs are a bit too long for the SIG’s stubby case neck, however.

Speer makes the 125-grain Gold Dot hollowpoint and TMJ FN bullets. Barnes produces the 125-grain XPB specially for the cartridge. Nevertheless, I tested several representative 9mm bullets from Sierra and Hornady, and these functioned perfectly and gave great accuracy and velocities.

The correct cartridge overall length (COL) for the .357 SIG is nominally 1.135 inches, and the test loads shown here are basically that. The industry maximum average pressure for the .357 SIG is 40,000 psi. The loads shown here exemplify the most practical ones. They were not designed to deliver the absolute top velocities, but they were exceptionally accurate and delivered uniform ballistics.