I use Hornady Zombie ammo. Its the same exact thing as their critical defense stuff, but a few bucks cheaper. As far as cycling in your gun, i have tested it in 4 different guns (Ruger SR9C, Springfield XD, Smith and Wesson M&P and a Glock) and i have never had an issue. I usually test with 5 or so rounds. Since the Hornady Critical Defense / Zombie ammo comes with 25 rounds in a box, this leaves you with 20 rounds to load with. 5 rounds usually gives you a good feel for a round's ability to cycle in your gun.