I doubt this will pertain to many people but just in case. I got a Alexander arms 50 beowulf upper recently. The upper comes with one magazine. Replacement mags are hard to find, cost in the $26-30 range. And many people complain about the tilting follower that likes to stick. Turns out the magazines are just metal AR magazines with slight modifications. the only difference is the front lip of the magazine has been ground down so that the head of bullet does not catch when chambering. Here is the alexander arms one on the top and my modified one on the bottom The red line here indicates where I had to modify Finally, replaced the follower with a magpul self-leveling follower so it does not tilt and get bound up when putting in rounds So a $30 mag can be made with a <$7 metal AR mag like one of these http://www.ammunitiondepot.com/D-H-Sabre-Tactical-30-Round-5-56-Magazine-p/mds10004.htm with a non-tilting follower for about $1.80 each http://www.midwayusa.com/product/23...-magazine-follower-ar-15-polymer-package-of-3 I did try a PMAG but the polymer is just not strong enough to hold the rounds in place and it starts to bow out.