With the ARC mags hitting the gun world someone has to be making or has found a way to retrofit a mag extension. My attemps to find one has led me to ask the forum where i can find one?
The MPA +4 round extenders for an Accurate mag fit on the bottom of the ARC magazine. However, I could only get 11 in the mag. I didn't get a chance to mess with it very long but the spring doesn't fit in the bottom of the extension right. I think you would have to modify the extension and since that is the only I have right now I wasn't willing to do that.