I was a KC-135 Tanker Driver. We qualified with Model 15's with 4" barrel. When we were flying in SEA, we had a big metal box with four Model 15's with 2" barrels inside and some ammo. The idea, if we had to bail out (nobody ever had to - the tanker was a reliable old bird), was to stick a revolver into the holster sewn into our survival vest. The vest contained a radio, extra batteries, mirror, day-nite smoke/flares, and a bunch of other goodies.
Perhaps not so well known is that we drew a revolver (M15 2")and ammo from the armory every time we were scheduled for a flight where we carried passengers - in the event of a hijacking. Thanks goodness we never had to use it, but it was there in the cockpit if it was needed.