Anyone have any experience with these mags? A local guy has a few for sale. I looked them up online to see what they were selling for and found a place that has a thousand plus still in stock for $19.95. The reason I want to know if they're any good is because on the description line it says word for word, "feeds perfectly, but will not drop free from most AR15 models". Any body have any feedback on this? I'm guessing its why they have so many left in stock.