Contact Craig Wheatley at www.tacticalinc.com (Tactical Innovations) and pick up some GI Grease Gun mags for $7.50 each. For an extra buck or so he'll modify the mags to work in the MAC. I bouught 6 of them the other day and they are a perfect fit. These M3A1 mags were new in the wrapper prior to his modifying and shipping them. You wont find a better deal out there. I actually saw USED M3A1 mags at a gun show the other day for $30! lol