The cheapest I've found was Monarch, which I believe is the Academy brand of outdoor stuff, for a little over $13/box, but it's not always in stock, go figure. I've also had a couple of hard primers with this stuff though, so for the dollar or two more CCI or WWB will do well. Also sometimes Federal's American Eagle brand is pretty cheap. I haven't had anything light-strike in well over a year (the few I had were in the first two hundred rounds with this gun). WWB is going to be the most consistently available & priced practice ammo you can find, IME.