Well, the search for a handgun is almost over. I have been going to a not so local shooting range and trying out some different handguns. The battle was between a Sig and Glock. After shooting with both guns, both being a 40 caliber, I have decided that I want a Sig. The handle is so much more comfy. The Sig I was using was a P226, very very sexy gun. Not a bad recoil, a little heavier in weight (which I like). Anyways, I'm still pretty new to this whole bullet caliber size. Was everyone as confused as I am when they first started getting into this stuff? Anyways, I have shot 9mm and .40 cal's. I'm not a big fan of the 9mm, I'm looking for something with more power.... Yeah, I'm a power hog. I know what you thinking, "can this guy handle it"...? Well, yes he can, I did very good for my first time out and even better my second and third. Anyway, I was hoping you guys could give me some insight. I have my eyes set on a Sig. I love the P226. I was wondering that if I get a bigger caliber gun, lets say the .45, would .40 ammo fit in it? Or .357? Or does only the specific ammo fit in its specific gun? I have been looking for a chart online with caliber sizes and what is bigger than what, what has more power, etc.. Basically how it all works. Can anyone help me?