Loading The .357 SIG

Along with both Hornady and Speer bullets, John prefers Power Pistol and
Accurate #9 as his powders of choice.

The .357 SIG has been around now for about 25 years. It’s a bottleneck cartridge, basically a .40 S&W necked down to .357. The very short neck is designed to use 9mm/0.355″ bullets but this does not mean .357 SIG cases can be made from .40 S&W brass. In fact the .357 SIG brass is slightly longer than the .40 S&W and shorter than the 10mm. The original idea was to come up with a cartridge equivalent to the .357 Magnum but at an overall cartridge length for use in standard-sized semi-autos.

Factory loads for the .357 SIG clock out at 1,325 fps from a pair of SIG SAUER pistols I have, one a 4.2″ 1911 and the other a 3.9″ Model 229 Legion. This load has a 125-gr. V-Crown JHP bullet. Checking the Black Hills 125-gr. JHP .357 Magnum through a 4.2″ Smith & Wesson Model 19 Combat Magnum results in a muzzle velocity of 1,350 fps — so there’s basically no difference.

As far as headspacing concerns go, I simply follow the directions coming with the Lee .357 SIG dies. When setting them as directed I have had no problem whatsoever with brass headspacing properly. When I first started reloading the .357 SIG I began by making dummy rounds to check for overall length. The industry standard seems to be 1.14″ OAL, however some magazines will accept longer loaded rounds and they will also chamber properly. Before loading a large amount of ammunition it’s a good idea to make dummy rounds first for checking.

I found out if cases were expanded and belled it was very likely the bullet would drop right into the case. There had to be a better way so I decided to try some cases that were full-length resized only and not expanded and belled. This solved the problem somewhat, however another problem resulted. If the case is not belled, most brass will be ruined when trying to seat square-based bullets.

With bullets having a standard base I use the Lee Universal Expander and just kiss the mouth of the case enough to allow the bullet to enter. Then the bullet is seated to the proper depth, resulting in the tight fit necessary. It takes a little extra effort to reload .357 SIG, as first the bullets must be seated and not crimped. Once bullets are seated to the proper length I use the Lee Collet Crimp Die, holding things in place nicely.

John uses Speer 115- and 125-Gold Dots, Acme coated 122- and 147-gr. FN bullets
and XTPs in 115-, 124- and 147-gr. weights. Cases are usually Starline.

Load Ideas

Brass is available from Starline, using small pistol primers. My powders of choice are Accurate #9, Power Pistol and Unique with the first two powders being used for full power loads. With Unique and Power Pistol I use #500 CCI Standard Pistol Primers, however, just as with sixgun loads, I switch to #550 CCI Magnum Pistol Primers with Accurate #9. My rule of thumb for handguns is to use standard primers on loads found on the burn rate chart up to and through #2400 and then switch to Magnum primers after that. Using Magnum primers with #9 in the .357 SIG results in much smaller extreme spreads.

My bullets of choice are the Hornady 115-XTP JHP, 124-XTP JHP and the 147-XTP JHP BT (boat tail). From Speer, I like their 115- and 124-Gold Dot HPs. My most-used factory load is the SIG 125-V-Crown JHP clocking out at 1,325 fps from my pair of SIG .357 SIG pistols. This load is duplicated with 8.7 grains of Power Pistol with either the Hornady or Speer bullets.

My most accurate reloads for the SIG .357 3.9" Model 229 Legion would be the Hornady 124-XTP and 115-XTP, both over 8.7 grains of Power Pistol, (1,330 fps and 1,325 fps); and the Hornady 115-XTP with 13.5 grains Accurate #9, clocking out at 1,374 fps. All loads will shoot into 1" for five shots at 15 yards.

Reloads in the SIG SAUER Model 1911 .357 SIG showed excellent accuracy,
and velocities right at the .357 Magnum at times.

The Status?

Several companies other than SIG SAUER have offered pistols chambered in the .357 SIG and there is a list of government and law enforcement agencies that have chosen it as a standard sidearm. However, many are returning to the 9mm for many reasons, recoil and muzzle blast being two. Just as with most other bottle-necked cartridges such as the .22 Jet, .256 Winchester, it’s never gone over in a big way with the shooting public.

For concealed carry use I prefer the lighter weight bullets, however with general outdoor use I will go with the 147-gr. JHPs as an alternative for the .357 Magnum with 158-gr. JHPs.

For more info: www.sigsauer.com, www.leeprecision.com

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