Windham Weaponry Interchangeable Kit Upper, 300 Blackout, 223, & 5.56mm

MSRP: $899.00


Shoot .223/5.56 and .300 blackout from the same upper receiver!

Only 1 left in stock

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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
– .223 Remington Caliber Barrel
– .300 AAC Blackout Caliber Barrel
– .223 Rem/300AAC Blackout Complete Bolt Carrier Group


– Caliber: .223 Remington / .300AAC Blackout
– Barrel: 16″ Chrome Lined 4150 Chome Moly Vanadium Steel
– Finish: Manganese Phosphate
– Barrel Style: Rifled appropriately for intended caliber, A2 Flash Hider
– Upper Receiver: CNC machined from Forged 7075 T6 Aircraft Aluminum
– Finish: Hard Coat Anodized Matte Black
– Bolts: Machined from Carpenter 158 Steel
– Color: Matte Black
– Railed Gas Block


– Fits: Standard Pattern AR-15 Lower Receivers

Manufacturer's SKU: KIT-MCS1

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Additional information

SKU: 300750

Weight6 lbs


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