I'm just going to throw this out there with three comments:
- This is a data compilation of 1180 LEO involved shoots, which of course includes all the things LEOs do going into places armed citizens with any sense or situational awareness avoid. (It's a safe bet the engagements that require more than a single magazine are calls where LEOs called for backup first).
- Percentage wise, calculated based on the second chart on page three, 6 rounds covers 75 percent of the total LEO involved shoots, 11 rounds (10 +1) covers 90 percent and 16 rounds (15 + 1) covers 97 percent. In other words, an armed citizen really has to be situationally clueless and or just plain looking for trouble (which is the point a not so armed citizen friendly prosecutor is likely to make when you are found to have had two spare high capacity mags on you, plus the one in the pistol) to find a situation where 16 rounds wont be enough.
- A spare mag makes sense as a means to quickly clear a couple uncommonly encountered types of malfunctions. A single spare is far more defensible from that perspective as it side steps the "just in case I needed more ammo" problem of "what were you doing there after dark?" issue. However, if you encounter one of those malfunctions in the the real world you chose your handgun poorly, and or did not adequately range test your pistol and carry ammo in advance (usually 200 rounds straight with no failures for a semi auto pistol).
In short, there are much better ways for an armed citizen to cover realistic real world contingencies than carrying three 15 or 17 round magazines.
https://www.policinginstitute.org/w...9/05/1.-OIS_incident_exec_summary_8.28.19.pdf