About some of the stats mentioned above. I used to study the NYPD Firearms Discharge Reports every time they came out. I've still got a couple floating around. With that in mind:
1. In the days of 2.? shots per engagement, they counted accidental/negligent discharges, suicides, putting down injured animals and, oh yeah, actual armed encounters. In short, every time some official firearm went "bang". That skewed the stats, so the system was changed.
2. Looking just at actual armed encounters, the range of average handgun shots per good guy/per bad guy runs 3.5-4.7 per shooting.
3. Looking just at actual armed encounters, the range of average handgun shots per good guy/per bad guy runs 6.?-8.? per gun fight.
4. Incidents involving multiple offenders/officers went above and beyond the above.
What I personally take from the above is that relying on 5-6 shots total isn't realistic. BTW, for those of us in rural areas, help can be a long way away in either/both distance and time. Extra ammo can be very comforting.
Over a long career I was issued/carried .38 Spl, .357 Magnum (125 gr Federal JHP), .40 S&W, .45 ACP, 9 mm & 10 mm (both full strength and down loaded). What I learned from that was that if you put bullets into vital system/structures, it didn't matter what you used. On the other hand, if you didn't hit vital systems/structures, it also didn't matter which one you used.