Stern Defense SD 4in MOD4 M-LOK 4in Barrel 9mm Black Complete Upper Receiver Black SDINBRLKK
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Stern Defense
Overview
The Stern Defense SD 4in Mod4 M-Lok Complete Upper Receiver is designed for the AR-9 platform, featuring a 4-inch barrel optimized for 9mm caliber. This complete upper receiver allows builders to easily assemble a compact and efficient setup, perfect for close-quarters engagements or as a lightweight option for various shooting applications. This upper is commonly found in builds that emphasize 9mm caliber performance.
Specifications
Stern Defense SD 4in MOD4 M-LOK 4in Barrel 9mm Black Complete Upper Receiver Black SDINBRLKK
Build history on GunPartPicker
Builders have been adding the Stern Defense SD 4in MOD4 M-LOK 4in Barrel 9mm Black Complete Upper Receiver Black SDINBRLKK to their builds on GunPartPicker since February 2026. All time, it ranks #457 of the 1,634 upper receivers builders have added.
Availability is good: it was in stock at one retailer or another nearly every day in August 2026, and today the one retailer we track has it in stock. Prices barely moved in August 2026, holding around $419.27, so there haven't been real sales lately. Buying today, the lowest price is $419.27 at Optics Planet, which matches the best price we saw in August.
Updated · from real builds on GunPartPicker · Prices checked · refreshed daily across 35 retailers
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Frequently Built With
The part most often added in each category by the 7 builds that include this one
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Build Configuration Breakdown
Aggregated and anonymized data showing how builders use this product
Gas SystemBased on real build data showing which gas system lengths builders use with this product.
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