Windham Weaponry’s RMCS-4 Rifle offers 4 Calibers in the same AR platform by simply changing out Barrels, Magazine Wells, and if necessary, the Bolt/Bolt Carrier and Magazine. Barrels are Chrome Lined for long wear and easy cleaning (except for 9mm Barrel with a Melonite finish) – machined from 4150 Chrome Moly Vanadium Steel, finished in Black Manganese Phosphate, and rifled appropriately for the intended caliber. Receivers are CNC machined from forged 7075 T6 Aircraft Aluminum and finished in Hardcoat Black Anodize. Bolts are machined from Carpenter 158 Steel. The key to barrel interchangeability is on the underside of the MCS Upper Receiver (see tech sheet).

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 caliber’s 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 appropriate caliber markings.