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Windham Weaponry Interchangeable AR-15 Upper Kit 300BLK/7.62×39 Upper

MSRP: $999.00


Switch between .300 Blackout and 7.62×29 with your standard AR-15 lower.

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Windham Weaponry is excited to offer it’s newest multi-caliber AR-15 convertible upper assembly. This exciting new development will allow you a huge leap in modularity for your favorite rifle, the AR-15. We all know that the AR-15 has become the most popular sporting rifle in American history and this Kit allows you to get hands on with other popular calibers and expand your AR-15 horizons. This revolutionary upper is designed to allow you to switch between barrels with great ease. Typically this task would have been impossible if not for the brilliant engineers in the Windham Weaponry R&D department. If you have been considering dabbling in other AR-15 calibers pick up one of these Windham MCS kits and see how easy the transition can be.


– Complete Flat Top Upper Receiver with integral railed fore end and proprietary barrel release lever and barrel retaining block
– .300 AAC Caliber Barrel
– 7.62x39mm Caliber Barrel
– .300 AAC Blackout Complete Bolt Carrier Group
– 7.62×39 Bolt
– 7.62×39 Magazine
– Note that the 7.62 Bolts are marked with 3 rings behind the locking lugs so as not to be confused with the .300 AAC caliber bolt.


– Caliber: 300 AAC Blackout/7.62x39mm
– Type: Complete
– Sights: None (Optic Ready)
– Barrel Material: 4150 Chrome Moly Vanadium Steel
– Barrel Description: Chrome-Lined
– Barrel Finish: Black Phosphate
– Receiver Description: 7075-T6 Aluminum
– Receiver Finish: Black Hard Coat Anodized
– Handguards: Quad Rail
– Handguard Finish: Black
– Purpose: Replacement

Additional information

Weight6 lbs

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Windham Weaponry Interchangeable AR-15 Upper Kit 300BLK/7.62×39 Upper for sale.

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Manufacturer's SKU: KIT-MCS-3

SKU: 300746

Product images are provided by the manufacturer and might not depict the actual product with 100% accuracy. Check the product description to verify it is exactly what you desire.

WARNING: This product contains a chemical known to the State of California to cause cancer. Also, drinking water and breathing heavily has been known to cause cancer by the state of California.

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