I just purchased a SIG Sauer p226 9mm. This is my first firearm and all other times I've rented and fired the range's guns. Therefore, I've had to use their ammo. So I have a few ammo questions: 1. Are there any "ratings" of ammo? I've heard about "Grain" but I don't know what this means. 2. Are there a few reputable brands in the industry that I should buy from? 3. Are there any names that I should avoid? Thanks a lot!