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SIG Sauer

SIG MPX K

Compact gas piston PCC with optimal barrel length balance

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Key Highlights

  • Gas piston soft recoil
  • 4.5-inch barrel
  • Timney trigger ready

Specifications

Price
$1,999
Weight
4 lb 14.400000000000006 oz
Calibers
9mm
Rail Type
mlok

Capability Profile

0-10 Scale Across 8 Axes

Compatibility Tags

family: pccmag-type: mpxinterface: picatinny-tophandguard: mlokbarrel: ultra-compact

Overview

The SIG MPX K represents the sweet spot of the MPX lineup, offering enough barrel length for reasonable velocity while maintaining compact dimensions. The 4.5-inch barrel provides approximately 200 fps more velocity than the Copperhead's 3.5-inch barrel while adding minimal length, making it the better choice for defensive applications where terminal performance matters.

The MPX's gas piston system shines in the K configuration. Unlike blowback PCCs that rely on heavy bolts and strong springs, the MPX uses expanding gases to cycle the action. This results in noticeably reduced recoil and a smoother shooting experience. The system also handles suppression well, with the gas regulator allowing tuning for suppressed or unsuppressed use.

SIG builds the MPX K with their KeyMod to M-LOK updated handguard, providing ample accessory mounting space for lights and lasers. The Timney trigger-ready fire control group allows easy upgrade to a premium trigger without gunsmithing. For shooters who want the MPX experience without the velocity sacrifice of the Copperhead or the length of the full-size, the K delivers the ideal balance.

Key Features

  • 4.5-inch barrel (better velocity than Copperhead)
  • Short-stroke gas piston operation
  • Folding stock/brace compatible
  • Adjustable gas regulator
  • M-LOK handguard with full rail
  • Timney trigger ready
  • AR-style controls
  • 30-round MPX magazines

Pros

  • +Optimal size/velocity balance
  • +Smooth gas piston operation
  • +Adjustable for suppressor use
  • +Timney trigger drop-in ready
  • +Quality SIG build and support
  • +Folding stock reduces storage size

Cons

  • Premium price point
  • Proprietary MPX magazines
  • Heavier than blowback alternatives
  • Gas system more complex
  • Magazines expensive

Detailed Specifications

caliber
9mm
Barrel Length
4.5 inches
Overall Length
17.9 inches (folded)
weight
4.9 lbs
Gas System
Short-stroke gas piston with regulator
barrel
Carbon steel, nitride finish
handguard
M-LOK full-length rail
trigger
Single-stage, Timney ready
msrp
$1,999

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