while reading various forum threads I've seen some guys say they found ten rounders for around $50 AR some places. One guy used a discount included with the rifle to buy a mag from Ruger. Probably like a 10% off coupon when you register or something.

There's also a "c-mag" product available but I have seen a few complaints and even a post saying flat out not to buy them. apparently not as reliable as the others.

I wonder if the magazines can be topped off (ammo added) while the mag is still inserted in the rifle? Also how hard is it to feed a single round with or without the magazine? With the length of the cartridge I would think it might be fairly easy to slip a round in the chamber and close the bolt to feed single rounds.