Just bought a new pistol grip for my AR-15, the grip has a compartment that has a slide shut lid. So I got to thinking about it and decided to make a survival kit that would be with my rifle all of the time. This is a list of what I was able to get in the compartment 4 #4 fish hooks 4 sinkers 12lb test fishing line 6 water/wind matches and strike side of the box 1 wire saw 4 pks of 2 water tabs button compass Not much but could make a bad situation a little better.
I would add an extra firing pin for your AR in there if it will fit. I keep extra lithium batteries in my compartment.
I was thinking about that I also have a small punch, flat scew driver and a phillips head short with flat handles. I carry my extra batteries in my front grip.
I've also been looking at this Magpul stock with a small storage compartment: ACS™ - Adaptable Carbine/Storage - ACS™ Carbine Stock – Mil-Spec Model It's not huge, but you could probably fit some maps & a compass, cleaning tools, or other similarly sized objects in there. I just bought a stripped DPMS lower for $125 out the door (no paperwork), so I think an AR will be my next project.