What .357 SIG is
SIG Sauer and Federal introduced .357 SIG in 1994. It uses a .40 S&W case necked down to hold a 9mm-diameter bullet, driven at high velocity. The goal was to match the performance of the well-regarded 125-grain .357 Magnum load in a semi-automatic pistol. The bottleneck case also feeds very reliably.
Who used it
Several agencies adopted .357 SIG, including the U.S. Secret Service and a number of state police departments. It had a reputation for good performance through barriers such as auto glass. Over the past decade, most of those agencies transitioned to 9mm. The Secret Service, for example, moved to a 9mm Glock. The drivers were the same as with .40 S&W: better modern 9mm bullets, lower recoil, higher capacity and cheaper training.
The Glock .357 SIG family
Glock's .357 SIG pistols share frames with their .40 S&W counterparts. In many cases a barrel swap converts between the two calibers, since both use the same magazines and case head; confirm with Glock before converting.
- Glock 31: full-size, the .357 SIG version of the Glock 22.
- Glock 32: compact, the .357 SIG version of the Glock 23.
- Glock 33: subcompact, the .357 SIG version of the Glock 27.
Glock 31 Gen 4
Full-size · .357 SIG
Glock 32 Gen 4
Compact · .357 SIG · 13+1
Glock 33 Gen 4
Subcompact · .357 SIG · 9+1
Pros and cons in 2026
| Pros | Cons |
|---|---|
| High velocity, flat trajectory | Ammunition costs more and is harder to find than 9mm |
| Reliable feeding from the bottleneck case | Sharper recoil and more muzzle blast |
| Good barrier reputation | Fewer agencies issue it, so less duty ammo is produced |
| Barrel swap with .40 S&W in many Glocks | Lower capacity than 9mm in the same frame |
The .40 S&W connection
Because the Glock 31 shares a frame with the Glock 22, the two calibers are closely linked. If you own a .40 S&W Glock, a .357 SIG barrel can be an inexpensive way to try the cartridge. Our .40 S&W article covers the parent cartridge and its future.
Glock 22 Gen 5
Full-size · .40 S&W
Who should buy one
- Shooters who like the cartridge and accept the ammo cost.
- Officers at agencies that still issue it.
- Collectors of law enforcement history.
For most new duty buyers, a 9mm such as the Glock 17 or 19 is the better choice. See our Glock 17 vs 19 guide.
Frequently asked questions
Is .357 SIG the same as .357 Magnum?
No. .357 SIG is a pistol cartridge on a necked-down .40 S&W case, designed to match the performance of a common .357 Magnum load.
Does the Secret Service still use .357 SIG?
The Secret Service has moved to a 9mm pistol, as have many agencies that once used .357 SIG.
Can I convert a Glock 22 to .357 SIG?
In many cases a barrel swap converts a .40 S&W Glock to .357 SIG, since they share magazines and case head. Confirm compatibility with Glock first.
Is .357 SIG ammo hard to find?
It is less common and more expensive than 9mm, though still produced by major makers.
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