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Sig Sauer
Overview
The SIG Sauer MCX Stock Adapter Kit is designed to allow builders to attach a standard carbine stock to their MCX platform. This adapter is compatible with Mil-Spec buffer tubes, ensuring a secure fit and reliable operation. It’s particularly well-suited for builds featuring a mid-length gas system and chambered in 5.56 NATO, making it a popular choice for those looking to enhance their rifle's versatility and ergonomics.
SIG Sauer MCX Stock Adapter KIT was the most added stock adapter on GunPartPicker in August 2026, ahead of the SIG Sauer Stock Adapter - 1913 Interface Folding Knuckle, with about 26% of all stock adapter parts added to builds. Up from #2 in July. Builds with this stock adapter are mostly chambered in 5.56 NATO (75%, then 300 Blackout 19%), split between mid-length (58%) and carbine-length (25%) gas systems, and mostly AR-15 (82%, then AR-10 15%).
Availability is good: it was in stock at one retailer or another nearly every day in August 2026, and today all 7 retailers we track have it in stock. The best price crept up from $135.51 to $158.43 over August 2026. Buying today, the lowest price is $125.43 at BattleHawk Armory, which matches the best price we saw in August.
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Updated · from real builds on GunPartPicker · Prices checked · refreshed daily across 31 retailers
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Aggregated and anonymized data showing how builders use this product
Builds in the community that include the SIG Sauer MCX Stock Adapter Kit
| Build | Parts | Total |
|---|---|---|
 | 30 | $6551.68 |
 | 31 | $7458.30 |
| 27 | $4253.00 |
 | 29 | $1876.13 |
 | 29 | $3881.88 |
 | 26 | $1180.48 |
 | 22 | $2362.21 |
 | 19 | $2810.27 |
 | 34 | $5701.96 |
| 19 | $3427.19 |
 | 37 | $4351.74 |
 | 25 | $1858.95 |
3 global ratings
Top reviews
SIG Sauer MCX stock adapter kit has a rubber butt pad that grips well to a shoulder or plate carrier. Mounts to the MCX receiver with the included hardware. Locks open and closed positively. Solid factory accessory for MCX builds.
adapter is precision machined, lockup against an MCX upper is tight with no play. swapped a few stocks through it without any wear on the adapter threads. sig spec quality
sig MCX stock adapter mates an MCX upper to a standard AR receiver extension via the adapter. cheek weld is comfortable for long range, QD socket on the rear is positioned correct for a sling pull
