The Sig Sauer MPX K (Sig part no. PMPX-4B-9-35) shrinks Sig’s proven MPX platform down to a 4.5-inch barrel, running a closed-bolt gas piston system that’s both ultra-reliable and durable. The MPX K is fully modular, accepting multiple handguard and barrel lengths, and ships ready to go for suppressor use with metric muzzle threading. The SIG PCB folding brace lets the K fold down into an ultra-compact size and remain operable even while folded, and an updated M-LOK handguard pairs with a Timney trigger for a crisp, consistent break. Finished in black hard-coat anodizing by Sig Sauer, this MPX K ships with a 35-round polymer magazine.

Key Specifications

• Chambered in 9mm, offering low-cost, low-recoil shooting in an ultra-compact package.
• Runs a 4.5-inch barrel, one of the shortest configurations in the MPX lineup.
• Cycles on a closed-bolt gas piston system for reliability and durability.
• Holds 35+1 rounds per magazine, and ships with 1 35-round polymer magazine included.
• Features the SIG PCB folding brace, operable even while folded for an ultra-compact carry size.
• Wears an updated M-LOK handguard for a clean, modular accessory-mounting surface.
• Runs a Timney trigger for a crisp, consistent break.
• Threaded in M13.5x1mm at the muzzle, ready for suppressor use.
• Equipped with a thumb safety for familiar, deliberate manual operation.
• Finished in black hard-coat anodizing for a durable, low-glare exterior.

Frequently Asked Questions

Can the MPX K fold for storage? Yes, the SIG PCB folding brace lets it fold down to an ultra-compact size and remains operable even while folded.

Is this pistol suppressor-ready? Yes, it ships threaded for suppressor use with a metric thread pattern.

What trigger does it use? A Timney trigger for a crisp, consistent break.

Buy the Sig Sauer MPX K Pistol, 9mm, 4.5-Inch, Folding Brace

The MPX K delivers Sig’s smooth-shooting gas-piston platform in its most compact, foldable form yet, ideal for discreet storage or transport. Order it from our AR pistols lineup at our Lubbock, Texas gun shop for fast, insured shipping to your FFL.