I recently bought my first AR-15 and am very pleased with it. But as I learn about all of the parts and internals of these guns I find myself wondering what spare parts I should keep in stock to make sure I can keep it running long-term. Kind of a prepping type idea. I want to have the most often replaced parts on hand in case for some reason something breaks and I can't just go online to buy another. (Or to make me less paranoid sounding, so I don't have to wait for the order to come through) Obviously it would be nice to just have a spare gun, but that's now quite what I had in mind. Any suggestions from people with experience wearing out parts on their ARs?