The (WS-MCR, Trademark Pending) Wolverine Supplies – Multi Caliber Rifle has been designed to be available in 5.56 NATO, 7.62 x 39 or .224 Valkyrie. We like the original AR180B "concept", so we went back to it and started fresh. We stayed with a modern CNC aluminium lower receiver. No need to reinvent the wheel, so we used that lower although we did add one very major improvement. We built in a rear take down pin, this eliminates the movement often found between the upper and lower and also strengths and stiffens the complete rifle.