Hello All, After reading Junho's inspiring post on building an AR (and JD's post dismissing the BS about building the AR) I've decided to take part in the fun, as long as money is in reach. I've got a few questions that are extremely noob, but I'd rather get laughed at online than in person I've never put much thought into how a firearm works, especially when it comes to the caliber of the weapon. Buy a 9mm, you have to use 9mm ammo. Buy a 12-gauge, and you cant use 20-gauge shells....pretty no-brainer. My first question (and I'm sure there will be more of them) deals with the above topic of caliber. In building this AR, I believe I'd like to use it for target shooting and also for hunting a range of game. The largest animal I believe I would go after would be deer. I certainly don't plan on taking on any elephants with this weapon. Perhaps the zombie hordes, if that day should come. I see there are a lot of 5.56, 7.62 (is this 'the same' as the .223??), and .308 fully assembled ARs for sale. Are these the primary or only calibers available? If so, which of those would be most suited for the largest of the animals? (ie Deer) My next question is, once I've decided upon a caliber, which parts are caliber dependent in the weapon, and which parts make no difference? I'm assuming the barrel and magazines are dependent on the caliber, but I'm not sure what else I need to be careful with. Thank you for your time and help. I can hardly wait!!