Sig Sauer MPX-K 9mm AR Pistol, 4.5 inch Threaded Barrel, Timney Flat Trigger, Ambidextrous Controls, M-LOK, 30+1
This compact Sig Sauer MPX-K stands out with its short-stroke gas piston system, 4.5 inch carbon steel threaded barrel, and fully ambidextrous controls. It features a factory Timney single-stage flat-faced trigger for a clean break, an alloy M-LOK handguard with a continuous top Picatinny rail, and a 1913 rear interface with a side-folding SIG PCB arm brace. Included SIG flip-up sights and two 30-round MPX magazines complete a well-equipped 9mm package made in the USA.
Condition
Overall Condition: Very good condition, showing only light, superficial signs of prior handling or use.
Bore Condition: Excellent - Clean, mirror finish, no signs of wear.
Bore Rifling: Excellent Rifling - Sharp lands and grooves.
Specific Condition Notes: Mild handling wear and light surface scratches are present. The pistol remains in great shape overall.
What’s Included
- Two 30-round SIG Sauer MPX polymer magazines
- SIG Sauer flip-up iron sights (installed)
- SIG PCB side-folding arm brace (installed)
The MPX-K configuration delivers a compact 9mm format with a 4.5 inch barrel and a short-stroke gas piston operating system paired to a locked, rotating bolt. The carbon steel barrel uses a 1:10 twist and is threaded M13.5x1 mm for compatibility with metric muzzle devices.
Ergonomics and control are strong points, with fully ambidextrous magazine release and manual safety, plus an AR-style charging handle for familiarity. The SIG polymer pistol grip and compact footprint make it easy to manage in close quarters.
The alloy M-LOK handguard provides versatile mounting options and integrates a continuous top Picatinny rail. The rear of the receiver features a 1913 interface, here equipped with a side-folding, single-strut SIG PCB arm brace for streamlined storage and transport. Factory SIG flip-up front and rear sights are installed.
A factory Timney single-stage flat-faced trigger offers a crisp, consistent pull. Capacity is 30+1, and this example includes two 30-round SIG MPX magazines. The hard-coat anodized finish and U.S. manufacture round out a durable, well-appointed MPX-K build. MFG part number is PMPX-4B-9-35.