I have some spares, AR 15 springs, e clips, pivots etc. I know a spare bolt, charging handle, etc, are also good. But what would you put away to keep your weapon and any you might recover working until the last of that 10,000 rounds of bullets and reloads are gone. Have waited for months for a firing pin on old 22 rifle and then had gun smith make one or might still be waiting. While my long term survival rate is poor I would like to hope that the firearms I have accumulated over the years will go on. Some of mine have been in family 80 to 130 years and some members will no turn them in. Always reading about perfect bug out bag, what about shooting parts bag? Laser batteries, backup sights once batteries no longer out there, broken shell extractor if you are forced to use cases 10 times and hope for the best.
It's always a good idea to keep spare parts around. We have extractors, firing pins, spring kits, etc for our SKS carbines, ARs and pistols. Even replacement springs and followers for our magazines.
Many parts manufacturers / retailers offer kits of the most often used, broken and lost parts for ARs. Some are for the fire control group, others for the uppers / bolt carrier groups. They'll usually list what's included.
Ammunition loaded with single base powder will last longest. If reloading for an AR15 there's little chance you will be able to find cases after 10 firings. I found they were good through 6 firings no problem, beyond that I figured they would get lost. If you don't have a case trimmer most cases will last 2 firings max. The main thing I lose is detents and detetent springs. To make the guns and brass last the longest need to get cycle speeds down especially on carbines and guns using silencers with some combination of adjustable gas block and heavier buffer.
I'd look at universal repair parts as well as model specific parts. You never know what you'll find. Small screw and spring selection can save lots of broken guns. Good exploded views of a large variety of firearms will help you put the inevitable "gun in a paper basket" back together. Jack First red, white and blue catalogs are good for this. A good quality set of files, drill bits and screw drivers are indispensable. Pin punches and a good quality fiber/brass hammer is handy. Lubricants, solvents and cleaning heat. Bore brushes for everything from .22 to 12ga, and stout cleaning rods that could push a stuck bullet from a squib round out. Having broken shell extractors for most major military cartridges is always a good idea. You may never need them, but when you do, you really need that.
