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SIG Sauer

SIG MCX/MPX Folding Magpul SL-K Stock and Adapter

Factory SIG SL-K folding-and-telescoping stock for the MCX and MPX, the SBR-conversion stock most MPX owners install once their tax stamp clears

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Quick Specs

Price
$300
Weight
1 lb
Brand
SIG Sauer
Category
stock

Features

  • Magpul SL-K stock
  • 1913 folding hinge
  • Telescoping length of pull
  • Locking hinge

Capability Boosts

CQB+1
Mobility+1

Recommended For

Vehicle Operations+2
Home Defense
Competition
Range Training

Compatibility Tags

family: pccplatform: sig-mpx-kplatform: sig-mpx-copperheadstock-interface: picatinny-1913

Overview

The SIG MCX/MPX Folding Magpul SL-K Stock with Adapter is the factory SBR conversion stock for SIG MPX K and Copperhead owners who have completed a Form 1 to convert their pistol-braced gun to a short-barreled rifle. The SL-K stock itself is the same Magpul SL-K used on AR-15 builds, mated to a SIG-built 1913-interface folding knuckle that locks the stock open under recoil and folds to the right side of the receiver for storage and transport.

Three benefits matter on an MPX. First, an actual stock with a fixed cheek weld is dramatically more usable for sustained shooting and accurate fire than the SB Tactical pistol brace it replaces. The SL-K is short, lightweight, and has a positive cheek-weld surface that keeps a red dot index consistent. Second, the locking hinge eliminates the wobble that plagued the original 1913 folding stock variants, which was the primary complaint about the early Sig folding hardware. Third, the stock telescopes to four positions, so a shooter wearing armor or a heavy jacket can extend the LOP for a proper shoulder index without resetting the gun.

This is the path most MPX K and Copperhead owners take post-tax-stamp. SIG sells the same hinge as a standalone 1913 adapter ($130) for shooters who want to pair a different aftermarket stock to the MPX, but the bundled SL-K kit is the price-competitive package most owners buy.

Compatible only with the MCX and MPX (and any host using the proprietary SIG 1913 interface). Cannot be installed on a pistol-braced configuration without a Form 1 SBR.

Key Features

  • Factory Magpul SL-K stock paired with SIG 1913 folding hinge
  • Locking hinge eliminates wobble of early variants
  • Folds to the right side of the receiver
  • Telescoping length of pull with four positions
  • Available in Black or Flat Dark Earth
  • Drop-on installation to the SIG 1913 rear interface

Pros

  • +Factory SIG fit and finish, no aftermarket compatibility surprises
  • +Locking hinge fixes the wobble problem of older Sig folding variants
  • +SL-K is light, compact, and has a real cheek weld
  • +Telescoping LOP works with armor or layered clothing
  • +Folds into a compact package for transport or storage

Cons

  • Requires a Form 1 SBR before legal installation in place of an SB Tactical brace
  • $300 MSRP, though street pricing typically lands $190-$216 at third-party retailers
  • Specific to the SIG 1913 rear interface, no AR-buffer-tube fitment
  • Some shooters prefer the A3 Tactical Skelestock for a lighter all-aluminum alternative

Detailed Specifications

stock
Magpul SL-K telescoping
hinge
SIG 1913 locking folding adapter
compatibility
SIG MCX, SIG MPX (all variants with 1913 rear interface)
foldDirection
Right side
lengthOfPull
Telescoping, 4 positions
weight
~16 oz total
colors
Black, Flat Dark Earth
legalNote
Stock attachment requires Form 1 SBR if replacing a pistol brace
msrp
$300

Compatible Platforms

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Add the SIG MCX/MPX Folding Magpul SL-K Stock and Adapter to your build and see how it enhances your platform.

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