Basically i have a utas xtr-12 12 gauge shotgun, which is the upper, sitting on a dpms ar 10 lower. I cant seem to find the 10rd mags for this weapon in stock anywhere, does anyone know what other brand magazines may work for this gun? I figure since its an ar-10 lower (magwell,etc) that there should be a wide variety of magazine available for it, but i cant seem to locate anything on it thru google. Any help would be greatly appreciated!