For the Kimber .380, I have 7+1 in the firearm and 6 rds in a spare mag. The extra mag is so small, it is easy to carry in your pocket, That’s 14 rds available for an encounter, which is equal to or more than most of the popular concealed carry weapons, especially the new “wonder 9’s.” I assuming most folks with double stack mags aren’t carrying an extra mag due to the mag’s bulkiness. Granted, I have to make a mag change which would be awkward and slow, but the reality is, that anything more than a few rounds for an encounter is very rare If you believe the statistics. Big shootouts just aren’t much of a reality, except in the movies. That could change, however, due to the crazy times that seem to be approaching.
I carry a 3 inch Kimber too.
An Ultra with 7+1, and two spare mags of .45 acp.
I carry the spares because under duress magazines can malfunction, which is far more common than an actual gun malfunction.
A wonder 9 with one mag becomes a paperweight if the mag fails.
Also train with your weapon.
Ask yourself how good are you REALLY with a 3 inch pocket rocket in a very high stress situation?
How about at 20 yards?
I dont carry spares to fight a huge gun battle.
I carry spares because predators are rarely alone, and shit happens under stress.
Situational awareness is the best SD tool you can have, but no body ever went through a SD shooting and said "I wish I had carried less ammo".