Honestly I was still in the mindset that guns rarely break and if they do I will just order the part. I saw the error of my ways when my OEM slide release broke on my glock and I didn't have the part to fix it, so it ended my range session.. pretty infuriating. Now I am pretty obsessed with knowing how my firearms work and having the knowledge/parts to fix them if they go down.
My primary AR went down at a class recently. I switched out the entire BCG, but a different problem reared up, so I switched to my backup AR and drove on. I believe in backups in depth:-)
Turns out that my bolt sheared two lugs. I've seen one lug break here or there before, but never two. Changing BCG's didn't help because one of the lugs got stuck in the lower and impeded the function of the hammer and sear. I've seen primers do that before, but never a bolt lug. Live and learn.
If you have the money....... Otherwise, a spare, complete BCG and buffer spring. Or at least a bolt and a buffer spring.
#RESIST