The 357 SIG vs. 357 Mag debate has cooled down over the years, but it’s always worth considering which cartridge is better for self-defense. After all, the .357 SIG was designed to deliver performance equal to that of the .357 Magnum – plus function optimally in a semi-automatic.
This article compares the relative performance of the two cartridges, including their recoil, stopping power, accuracy, and overall cost. It’s all in service of helping you determine which round is better suited to your needs.
What’s the Difference Between 357 SIG and 357 Mag?
The greatest difference between these two rounds is the type of firearm they are designed for. The 357 SIG was created for semi-auto handguns, whereas the 357 Mag was intended for revolvers (though it was later adopted in lever-action rifles).
While these rounds are similar to one another, one may very well prove better than the other under certain conditions. Let’s begin by reviewing the differences in these cartridges’ specifications. We’ll then see how those differences impact real-world performance.
Cartridge Specifications
SIG Sauer designed the 357 SIG to emulate the 357 Mag’s performance. Despite this, they did not choose the 357 Mag as their new round’s parent case. They gave that honor to the 10mm Auto; an appropriate choice, given SIG’s goal of distilling big revolver energy into a semi-auto cartridge. (For reference, the much older 357 Mag’s parent case is the 38 Special.)
The 357 SIG is loaded with a 0.355” diameter bullet. True to its name, the 357 Mag fires a 0.357” diameter bullet. The neck diameter of the 357 SIG is 0.381”; the 357 Mag, 0.379”.
The 357 SIG has a larger base diameter than the 357 Mag: 0.424” and 0.379” 357 Mag, respectively. The 357 Mag has a longer case: 1.290”, which is 0.425” longer than the 357 SIG (0.865”). Its longer case gives the 357 Magnum an overall length of 1.590”. At 1.140”, the 357 SIG is a pipsqueak by comparison.
The 357 Mag’s longer case has more capacity: 26.2 grains H2O, compared to 19.6 grains H2O for the 357 SIG.
The 357 SIG’s maximum chamber pressure is higher: 40,000 psi, versus 35,000 psi for the 357 Mag.
Let’s see how these cartridges’ specs affect their real-world performance, beginning with how hard each one kicks.
Recoil: 357 SIG vs. 357 Magnum
I always compare recoil because it’s one of the first things a shooter asks about when firing a new cartridge. We all want to know how much the round kicks.
Many shooters fret about recoil – not so much because of physical pain (though this can be an issue), but more so for initial accuracy and follow-up shots. Compared to a cartridge with less recoil, one with more will kick the muzzle off the target more with each shot. This can slow follow-up shot placement, as well as cause the shooter to develop a flinch which further impairs marksmanship.
The less recoil you feel, the more accurately you can fire. Less recoil is always better (unless you’re a macho man who has to prove how tough you are to the world).
Felt recoil is subjective. It varies from shooter to shooter. That’s why I base my comparisons on free recoil energy, an objective measure determined by four factors: projectile weight, propellant weight, muzzle velocity, and firearm weight.
When a 357 SIG 125 grain bullet is fired at 1,350 fps from a 2-pound pistol, it has about 9 ft-lbs of recoil. Most consider it to have stout, snappy recoil.
When a 357 Mag 125 grain bullet is fired at 1,450 fps from a 2-pound revolver, it has about 10 ft-lbs of recoil.
While the 357 Mag generates more recoil energy than the 357 SIG, it’s not significant enough for most shooters to tell the difference. This section is a tie.
Accuracy
It’s important to remember that accuracy is more often a function of the (A) shooting platform or (B) shooter than it is of the (C) cartridge. The ammo, bullet design, firearm pairing, environmental conditions, trajectory, recoil, and shooter all play significant roles in determining how much accuracy a cartridge can exhibit.
When fired from handguns, these .357 caliber cartridges are highly accurate within close ranges up to 50 yards. A skilled marksman may hit their target at 100 yards with either pistol. The 357 Mag can be even more accurate when it is fired out of a lever-action rifle, although that just reflects the chief advantage of a rifle. With a longer barrel comes a bullet with a higher muzzle velocity and greater gyroscopic stability.
This section is also a tie. Accuracy is ultimately determined by the shooter, firearm, and ammo pairing, and these cartridges are similar by design.
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