Sig Sauer MPX K 9mm Luger Pistol, 4.5" Threaded Barrel, Short-Stroke Gas Piston, Ambi Controls, 4x 30-Rd Mags
This Sig Sauer MPX K is the compact, micro-size 9mm variant built around a short-stroke gas piston system with AR-style ambidextrous controls. It features a 4.5" threaded barrel capped with a three-prong flash hider, a hard-anodized alloy receiver with a Picatinny rail on the upper, and a slick-top KeyMod handguard that uses a short add-on Picatinny segment up front for the flip-up sight. It comes ready with a SIG-branded stabilizing brace on the rear 1913 interface, flip-up iron sights, and four factory 30-round MPX magazines.
The MPX K stands out for its closed-bolt, rotating-bolt operating system and its user-friendly control layout, including an ambidextrous safety selector and magazine release with AR-style bolt catch/release. The aluminum KeyMod handguard offers mounting flexibility with KeyMod slots at 3, 6, and 9 o'clock and diagonal vent cuts, plus an installed KeyMod Picatinny rail section under the handguard. Built in the USA, this example pairs compact dimensions with dependable gas piston operation and proprietary MPX magazine compatibility.
Condition
Overall Condition: Good condition, showing some signs of prior use and handling.
Bore Overall Condition: Good - Clean, well-maintained, minor wear marks.
Bore Rifling: Good Rifling - Intact, well-defined lands and grooves.
Specific Condition Notes: The upper and lower receivers display notable scratches and blemishes from prior handling and use. The accessory rails show finish blemishing.
What’s Included
- 4x 30-round SIG Sauer MPX factory polymer magazines with steel feed lips
- SIG-branded pistol stabilizing brace on rear 1913 interface (installed)
- Flip-up front and rear iron sights (installed)
- KeyMod Picatinny accessory rail section mounted under the handguard (installed)
- Three-prong flash hider (installed)
The MPX K uses a short-stroke gas piston operating system with a closed bolt and rotating bolt, designed for reliable cycling with 9mm Luger. Right-side ejection and AR-style manual of arms make it familiar and efficient to run.
The 4.5" barrel is threaded and fitted with a three-prong flash hider. A 1:10 twist supports common 9mm bullet weights, and the included flip-up iron sights are ready for immediate use.
The receiver is alloy with a hard-anodized finish and a Picatinny rail on the upper receiver. The slick-top aluminum KeyMod handguard lacks a full-length top rail and uses a short add-on Picatinny segment at the front for the flip-up sight; it includes KeyMod slots at the 3, 6, and 9 o'clock positions with diagonal vent cuts, plus an installed KeyMod Picatinny accessory rail section under the handguard.
Controls are fully ambidextrous, including the safety selector and magazine release, with an AR-style bolt catch/release. The rear 1913 interface hosts a SIG-branded pistol stabilizing brace with a rubber construction for comfortable support.
This MPX K feeds from proprietary SIG MPX magazines and has a 30+1 capacity. It is made in the USA and includes four factory 30-round magazines to keep you running longer between reloads.