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Questions & Answers
Can this also be used as a stock adapter if need were it connects Expert Answer

Yes, the stock, and even the buffer tube under it can both be removed to use this adapter on other stocks.

by Ethan C., Gear Expert, May 15, 2018
Does this fold flat or does it fold in an angle to the receiver? Expert Answer

The SIG SAUER MCX/MPX Side-Folding M4 Style Stock will fold flat to the side of the receiver on your MPX/MCX rifle.

by Ethan, Gear Expert, January 10, 2023
Customer Reviews
Helpful Positive Review
Very nice quality, fits perfect. by Shoe, January 8, 2024
I was afraid this Sig stock would be too bulky but fits my MPX perfectly and makes it a more comfortable gun to shoot. The closing latch is stiff and a little difficult to close but I’m hoping it will ease up with use. For me it’s an improvement ov...
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1/1 found this helpful
Helpful Positive Review
Nice solid pic-mount folding stock by BenM, Verified Owner, April 27, 2024
Got this to replace the non-adjustable stock that came on my JAKL. The folding mechanism was pretty well stuck at first but I eventually got it loose and folding. The stock mounted easily and it looks great, plus now I have an adjustable length-of-pu...
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1/1 found this helpful
Helpful Positive Review
Great Stock for MCX by Elconejogrande, May 3, 2018
Another excellent product from Sig Sauer. I own every stock made for the MCX and this is by far my favorite. I bought this for my MCX 300 blk. Having the xtra mag allows me to have both Super Sonic and Sub Sonic Ammo at my fingertips. Very well made ...
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2/2 found this helpful
Helpful Positive Review
Great Folding Stock by Scotty, August 6, 2020
Purchased the Sig MCX folding stock for my Ruger PC9 (gen 3). Stock fit and finish is good and it fit the rifle very well. While having a folding stock is a matter of personal taste, I am very pleased with the way the rifle can be taken down and fi...
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1/1 found this helpful
Helpful Positive Review
M4 stock for MPX by Schweinmesser, January 22, 2017
Great M4 style stock to replace the retractable stock that came with the MPX Carbine making it feel more familiar. Easy to install and adjust. The folding capability is nice. Been using it in USPSA competitions and it feels very sturdy. Great price a...
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5/5 found this helpful
Helpful Positive Review
Great Stock by Mg77, Verified Owner, July 17, 2020
Purchased this for a Ruger PC Charger and it works perfect. I purchased another folding stock made by Sig and was not happy with it as the length was to short. I love the fact this can be used on an AR or a 1913 rail. Excellent purchase, especially w...
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1/1 found this helpful
Read All 14 Reviews
Gun Model:
SIG Sauer MCX, SIG Sauer MPX
Color:
Black
Finish:
Nitron Black
Hand:
Ambidextrous
Length:
Adjustable
Weight:
1.1 lb
Buffer Tube Size:
Mil-Spec
Additional Features:
Mil Spec-AR Buffer Tube
Included Accessories:
Adjustable Stock, Swivel Knuckle, Torq Adjustable Mount for 1913 Rail
Condition:
Factory DEMO
Stock/Brace Material:
Aluminum, Plastic
Fabric/Material:
Metal & Plastic

Code: SD9-RSF-STKXFOLDM4BLK-DEMO

MPN: STOCK-X-FOLD-M4-BLK-DEMO

Product No Longer Available

Product Info for SIG SAUER MCX/MPX Side-Folding M4 Style Stock Black - All NFA Rules Apply STKXFOLDM4BLK

The Sig Sauer MCX/MPX Side-Folding Butt Stock makes your MCX or MPX easier to pack into smaller spaces. These Rifle Stocks deliver all the SIG SAUER quality you expect, with solid installation and a stable feel when shooting. Sig Sauer MCX/MPX Compact Side-Folding Stocks mount easily on your receiver's 1913 interface. Customize your build with a sleek look with a Sig Sauer MCX/MPX Side-Folding Rifle Stock.image

Features of SIG SAUER MCX/MPX Side-Folding M4 Style Stock STOCK-X-FOLD-M4-BLK:

  • Sturdy folding M4-style stock.
  • Allows installation of standard AR-15 type buttstocks on your MCX/MPX.
  • Adjustable length of pull.
  • Easy to install.

Package Contents:

  • SIG SAUER MCX/MPX Side-Folding M4 Style Stock Black - All NFA Rules Apply STKXFOLDM4BLK

5.56x45mm NATO Ammo

1–25 / 25
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Gun Parts and Accessories

1–39 / 39
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.300 AAC Blackout Ammo

1–23 / 23
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Firearm Case

1–30 / 30
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Magazine and Accessories

1–14 / 14
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Related Products to SIG SAUER MCX/MPX Side-Folding M4 Style Stock Black - All NFA Rules Apply STKXFOLDM4BLK

SIG SAUER MCX/MPX Side-Folding M4 Style Stock Black - All NFA Rules Apply STKXFOLDM4BLK Unavailable & Discontinued Models

List of Unorderable Models

  • DEMO, SIG SAUER MCX/MPX Side-Folding M4 Style Stock Black , MPN: STOCK-X-FOLD-M4-BLK-DEMO , Code: SD9-RSF-STKXFOLDM4BLK-DEMO
  • USED SIG SAUER MCX/MPX Side-Folding M4 Style Stock Black, EDEMO2, Used, Condition Like New , MPN: STOCK-X-FOLD-M4-BLK-EDEMO2 , Code: SD9-RSF-STKXFOLDM4BLK-EE-EDEMO2
  • USED, SIG SAUER MCX/MPX Side-Folding M4 Style Stock Black , MPN: STOCK-X-FOLD-M4-BLK-EDEMO , Code: SD9-RSF-STKXFOLDM4BLK-EDEMO-IN-C
  • SIG SAUER MCX/MPX Side-Folding M4 Style Stock Black , MPN: STOCK-X-FOLD-M4-BLK , UPC: 798681544042 , Code: SD9-RSF-STKXFOLDM4BLK-EE
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Last updated 2026-10-02 UTC.