Earlier, I showed how a 10.5 or 11" AR pistol can be broken down to fit in a standard computer backpack or assault pack size. As you see, there's also room for a sidearm and spare mag. This was my idea of an insurance bag for a place where I wasn't expecting any trouble, but was somewhat isolated, so if there was an emergency, it might be up to an hour before LEO arrived.
Using the AR-like FM15 gives different options. The beauty of a large bufferless pistol or SBR like this, is the ability to be more compact than an assembled AR15 pistol, yet ready for action in just a couple seconds. Unzip the bag, extend the stock or brace-
if there's time- safety off, engage threat. However, an assembled AR15 -style pistol is "lumpier" than a dissembled one. You'll need a larger bag, like this Cannae Sarcina 34L bag, to comfortably fit the FM15. That does, however, give additional options. This "base load" has my FM15, a sidearm, and 160 rounds of 5.56mm, and 66 rounds of 9mm with sidearm and holster.
In an emergency, I can grab this and go, and have what I need to get my family out of dangerous situations like the mobs we've seen in the last few years. If I have the luxury of time, I can choose some additional items to add, like a couple of changes of clothes. If I'm going on vacation, I would probably lose most of the spare mags, and the 50-rd box of Federal +P+ JHP, and add more clothes. If things were going super bad, I could quickly add 6 more AR mags and more water, and run.
(If you have poor eyesight, the Sarcina contents also include wet wipes, lights, hygiene kit, cigars, a poncho liner lightweight "blanket", playing cards, Swiss Army knife, multitool, compact GE fighting knife, Camelback 1L water bottle, 2 kinds of sonic ear pro- allowing normal hearing, but protection from loud noises- and titanium chopsticks.)
AR15 pistols are easily found, and there are budget versions available. They work great, as long as members have the time to pull out the receivers and assemble them. Newer bufferless AR15 evolutions like the FM15 require a larger bag to carry assembled, but can be ready in barely more time than it takes to present a sidearm from a holster.
John