PSA GEN4 4" 9mm 6" Lightweight M-LOK Railed Upper - With BCG & CH
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Palmetto State Armory
Overview
The PSA Gen4 4" 9mm Lightweight M-Lok Railed Upper is a complete upper receiver designed for the AR-15 platform, featuring a compact 4-inch barrel that offers excellent maneuverability for close-quarters applications. With a thread pitch of 1/2x28, it allows for easy attachment of muzzle devices, enhancing versatility for the builder. This upper is commonly used in pistol builds where a shorter profile is preferred, making it ideal for tactical or home defense setups.
Specifications
PSA GEN4 4" 9mm 6" Lightweight M-LOK Railed Upper - With BCG & CH
August 2026 on GunPartPicker
PSA GEN4 4" 9mm 6" Lightweight M-LOK Railed Upper - With BCG & CH ranked #291 of the 690 upper receivers builders added on GunPartPicker in August 2026. Builders have been adding it to their builds on GunPartPicker since March 2026. All time, it ranks #373 of the 1,633 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 $319.99, so there haven't been real sales lately. Buying today, the lowest price is $319.99 at Palmetto State Armory, 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 4 builds that include this one
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