Primary Weapons Systems MK1 5.56x45mm AR Lower, Black - 222M100RM1B
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This is a serialized firearm.
Primary Weapon Systems
Overview
The Primary Weapons Systems MK1 5.56x45mm AR Lower is a complete lower receiver designed for the AR-15 platform, crafted from durable 7075-T6 aluminum, and finished in black. This lower is compatible with the 5.56 NATO caliber, allowing builders to create reliable and precise rifles suited for various shooting applications. It is commonly used in builds featuring a mid-length gas system, making it an excellent choice for those looking to balance performance and recoil management.
Specifications
Primary Weapons Systems MK1 5.56x45mm AR Lower, Black - 222M100RM1B
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September 2026 on GunPartPicker
Primary Weapons Systems MK1 5.56x45mm AR Lower, Black - 222M100RM1B ranked #248 of the 477 lower receivers builders added on GunPartPicker in September 2026. Builders have been adding it to their builds on GunPartPicker since March 2026. All time, it ranks #522 of the 1,005 lower receivers builders have added.
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Frequently Built With
The part most often added in each category by the builds that include this one
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Build Configuration Breakdown
Aggregated and anonymized data showing how builders use this product
CaliberBased on real build data showing which calibers builders choose alongside this product.
Gas SystemBased on real build data showing which gas system lengths builders use with this product.
Builds Featuring This Part
See all 1 →Builds in the community that include the Primary Weapons Systems MK1 5.56x45mm AR Lower, Black - 222M100RM1B
| Build | Parts | Total |
|---|---|---|
 | 11 | $3251.62 |
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