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Windham Weaponry RMCS-4 Multi-Caliber AR-15 Platform Rifle, 16" Barrel, 30 Rounds, Black

Windham Weaponry
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Typically ships within 5 to 7 business days when a valid FFL is received
  • All firearm sales are final. NO RETURNS.
  • Return to manufacturer for warranty service.
  • Actual buyer must pickup from FFL dealer who will conduct the background check. Learn more
  • Firearm transfer must be the actual transferee/buyer. Click here to see BATFE form "Transaction Record Part 1".
  • Firearms are only available for purchase online.
A $10 handling fee will be charged per order. No additional charge for multiple firearms on an order.

The revolutionary Windham RMCS-4 AR rifle allows you to switch between calibers with ease.

Windham Weaponry's design is a massive leap in modularity for the popular AR-15. This rifle allows plenty of options for the survivalist or prepper in case one type of ammo becomes scarce or expensive, as the gun can shoot 5.56mm NATO/.223 Remington, .300 AAC Blackout, 7.62x39mm Soviet, or 9mm. Windham's brilliant engineers made switching out the barrel, magazine wells, and bolt/bolt carrier simple. Pick up this rifle and multi-caliber kit to see how smooth the transition can be.

The key to barrel interchangeability is on the underside of the MCS Upper Receiver. Once the Barrel Retaining Block is unlatched and moved forward, the Barrel Retaining Arms rotate out to release the barrel, ready to be replaced with the barrel of caliber choice. In the MCS Lower Receiver, magazine interchangeability is as easy as dropping the trigger guard and pushing in the Mag Release Button. One calibers mag well slides off, and another is substituted. Then, if required, the appropriate Bolt Carrier is inserted into the Upper, and with an appropriate magazine and the correct caliber ammo to match the barrel, the rifle is ready to fire. All WW barrels are clearly stamped with compatible caliber markings.

Visit our AR-15 Parts and Accessories section to further customize this AR-15 with the best selection of attachments and upgrades online.

Windham Weaponry RMCS-4 AR-15 Platform Rifle Features and Specifications:

Platform Base: Complete MCS M4 Profile Rifle, Chambered in 5.56mm NATO with BCG capable of 5.56 mm NATO/.300 AAC Blackout)
Barrels: (4) Each 16", 4150 Chome Moly Vanadium Steel, Manganese Phosphate Finish
*Each Barrel Rifled Appropriately for Intended Caliber
- 5.56mm NATO/.223 Remington Barrel Assembly, Chrome-Lined Barrel
- .300 AAC Blackout Barrel Assembly, Chrome-Lined Barrel
- 7.62x39mm Soviet Barrel Assembly w/ Bolt Carrier, Chrome-Lined Barrel
- 9mm Barrel Assembly w/ Blowback Bolt Carrier, Melonite-Lined Barrel
Bolts: Machined from Carpenter 158 Steel
Muzzle Device: A2 Flash Hider
- AR-Type Magazine, 30 Rounds (5.56/.223/.300)
- AK-Type Magazine, 30 Rounds (7.62)
- Colt-Type Magazine, 20 Rounds (9mm)
Magazine Wells:
- AR-Type Mag Well (.223/5.56/.300/7.62)
- AK-Type Mag Well (7.62)
- Colt-Type Mag Well (9mm)
Upper Receiver: MCS Flat Top with Integral Railed Free Float Forend, Hardcoat Anodized CNC-Machined Forged 7075 T6 Aircraft Aluminum
- Key to Barrel Interchangeability is on the Underside of the MCS Upper Receiver
Lower Receiver: MCS
Stock: Telescoping
Gas Block: Railed
Overall Finish: Matte Black

Also Includes:
Heavy Duty Lockable Rifle Case w/ Custom Die-Cut Foam

NOTE: This item is oversized or heavy and is subject to a "Bulk Fee". The fee will be added to your cart at checkout.
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  • Select a local Federal Firearms Licensed (FFL) Dealer that will accept the firearm and complete the transfer. Find a FFL Dealer HERE.
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  • Pick up your firearm from the FFL Dealer, who will need to do a criminal and mental health background check. Transfer fees may apply.
Buying Firearms on the Internet

Federal law requires firearms to be shipped to FFL Dealers. For an individual to receive a firearm from Cheaper Than Dirt! it must be shipped to an FFL Dealer in your state.

Locating a Federal-Firearm License Dealer (FFL) in Your Area

There are thousands of FFL Dealers in the United States. You may choose an FFL Dealer from our preferred listing or you may find a dealer in your area. To find a list of FFL Dealers in your area area CLICK HERE. If you choose a dealer that is not on our preferred list, either you or the FFL Dealer will be required to submit a copy of the Federal Firearms License referencing your Cheaper Than Dirt! order number. The FFL Dealer will usually charge a fee to conduct the transfer. There are duties that the FFL Dealer is required to do during the process which include a criminal and mental health background check through NICS. Remember, the FFL Dealer is doing you a favor and the process takes time to complete. Fees can vary so check with the FFL Dealer ahead of time to request a quote on the fees associated with your firearm transfer. The FFL Dealer is in business to make a profit and your internet purchase may be viewed as competition to their retail business. If you feel the fees are too high, you can search for another FFL Dealer.

Completing the Transaction

Once you place the firearm in your cart and checkout you will receive a confirmation email that has your order number and further instructions. We will verify the FFL license and also make the FFL Dealer aware that an order from Cheaper Than Dirt! will soon be arriving for you. Most orders are processed within 2-3 business days from the time we receive and verify the FFL Dealers information. Once shipped, your firearm will arrive at the FFL Dealer within 3-7 days business days. The FFL Dealer will begin processing the shipment. It may be an additional day or so before the FFL Dealer is ready to conduct the transfer of the firearm to you. Call the FFL Dealer and set an appointment to confirm that the firearm is ready to be transferred.

Please note! All Firearm Sales are Final

It is important to thoroughly inspect your firearm before completion of the transfer. Once the firearm is transferred into your name, Cheaper Than Dirt! will not accept a return or exchange under any circumstance. If a defect is discovered after completing the transfer, you must contact the manufacturer directly for repair or replacement.