SIG Sauer MPX-K No-Brace 9mm AR Pistol, 4.5 in Threaded Barrel, Short-Stroke Gas Piston, 35+1, M-LOK, USA
This SIG Sauer MPX-K No-Brace 9mm delivers the compact MPX format with a 4.5 inch threaded barrel, fully ambidextrous controls, and a short-stroke gas piston with a closed rotating bolt. It includes three 35-round factory MPX magazines and an installed Radian Raptor-LT ambidextrous charging handle. The top rail runs continuously across the receiver and handguard, and the pistol ships in the factory SIG box labeled 31-Oct-2023.
Condition
Overall Condition: Very good condition, showing only light, superficial signs of prior handling or use.
Bore Overall Condition: Excellent - Clean, mirror finish, no signs of wear.
Bore Rifling: Excellent Rifling - Sharp lands and grooves.
Specific Condition Notes: Light finish wear is present on high-contact points such as the charging handle and Picatinny rails. The short-stroke gas piston system is clean and the action cycles smoothly. The factory box label is dated 31-Oct-2023.
What’s Included
- SIG Sauer factory cardboard box with serialized label
- Three (3) 35-round SIG Sauer MPX polymer magazines
- Radian Raptor-LT ambidextrous charging handle (installed)
The MPX-K submodel brings a compact 4.5 inch barrel and a no-brace configuration with a rear 1913 Picatinny endcap. Its continuous 1913 top rail spans the receiver and handguard, providing uninterrupted mounting space while maintaining a streamlined profile.
The operating system is SIG’s short-stroke gas piston with a closed rotating bolt. This design is engineered for reliable cycling with 9mm ammunition while keeping fouling directed away from the receiver.
The cold hammer-forged barrel is threaded M13.5x1 mm and comes with a three-prong flash hider installed. A 1:10 twist rate supports common 9mm bullet weights, and the aluminum M-LOK handguard keeps the front end light and rigid.
Controls are fully ambidextrous, including the bolt catch/release, magazine release, and safety selector. The Radian Raptor-LT ambidextrous charging handle enhances manipulation from either side, and the flat-faced trigger offers a straight pull profile.
Construction centers on an aluminum receiver set with a SIG polymer pistol grip. Capacity is 35+1 rounds, and this example is made in the USA. The factory part number is PMPX-4B-9-NB, with the box label dated October 31, 2023.