But you need parts for those...i guess buying 5 more AR's aren't unreasonable.
I never thought about that until now. Which made me think about my P10C bullet proof firing pin I bought because there are a good handful of peoples who's firing pins broke. Same problem Glock had. I got a new handgun bag and was going to put the spare pin in there. I forgot where I put it and took me 3 months to find. It was in my old Magpul Stock box that had the milspec spare stock in it. So even though it was with all my gun stuff, I couldn't find the damn thing for 3 months. I was super close to ordering another one.
I'll give up on my spare parts venture for now.
My initial feedback was partially in jest, but mostly serious. Over the years, I have accumulated a bunch of spare parts for ARs as well as handguns. I have backups for my ARs as well as Glocks. In general, they are pretty reliable, but have their share of "wear items". When I first got into ARs, I bought a spare BCG, bolt, firing pin and other items that I heard can shut down a gun. That said, there are many other smaller parts that can render a gun useless. Many of those smaller parts, like springs, detents and such require tools and a bit of time to replace (like FJ mentioned). I do have complete LPKs that I could use as backup, but I mostly got them on sale or for another lower.
In general, I buy parts as they fail or become questionable. I also have bought parts to address specific things, and at the same time bought extras just in case (like springs that are notorious for going flying) and have since lost track of them. Thankfully, the AR parts were relatively inexpensive and if I should need them again, I can order more.
For Glocks, I only have spare action springs. That was because I bought a couple extra when I had to replace one. I have thought about buying the "critical" parts set that they sell on many sites, but just haven't gotten around to it. As mentioned, it can be quite expensive to keep a range of spare parts. Thankfully, Glock parts are easy to come by and through many different vendors.