Randomly occurring low-probability events with no causal relationship have no reason to increase in probability as a function of a "life and death struggle"...
Carry a crap gun and that changes, now FTE, FTF, etc... have a causal relationship - crappy gun... Don't do that... Practice, test, don't scrimp.
No, I don't mean that literally "if it can go wrong it will go wrong in a gunfight." What I'm saying is that at the range, you'll probably go out on a sunny day in good lighting conditions, you won't be tired, sick, or uncomfortable, it's an environment that you know and are familiar with, there's little stress. If you're using Shoot-N-C targets you'll have a visual confirmation that you hit the target when you shot, you'll take care not to scratch your gun or get your pants dirty... I know that many of these are generalizations, but for many people it's true.
In a violent life or death struggle, you may not start from 21 feet away and work your way forward. It might start as a sucker punch to the back of the head or a knife in your stomach, or two guys grabbing you while their friend grabs your wife by the hair. You may very well get hit or hurt before you get your gun into the equation, the gun might get banged around, stepped on, dropped in a puddle or pile of sand before you shoot, or halfway through the mag. Bodily fluids like spit, sweat or blood may interfere with your grip, or smacking that SOB in the forehead with the butt of your pistol might break or damage the magazine floorplate, or give the magazine spring that extra push it needed to not raise the follower correctly.
I was saying that anything can happen in a violent struggle which would increase the odds of a weapon or shooter malfunction, and that when preparing for a violent struggle you should prepare for an unpredictable violent struggle, not the canned scenario where your gun works flawlessly everytime and the bad guys in the mirror don't cash the check that your tough guy talking just wrote.
For example, I saw a dashcam video of a female cop in North Carolina who was shooting it out with a guy in a minutes long moving gunfight, he was fleeing a bank robbery with an AR-15. She took several hits in the fight, including one to the right forearm (her primary shooting or "strong" side) at the start of the gunfight, which made it so she couldn't properly grip her gun. While shooting, the gun jammed due to her injury; I saw another video of her describing what took place, but either she didn't say exactly what it was that caused it or I don't remember, as it's been a few years since I saw the videos.
While moving (to stay behind the engine block of her rolling cruiser which she was using as limited cover) and wounded and
still taking fire, she had to clear the malfunction and keep fighting. I believe that she dropped the partially full mag on the ground, then cleared the jam and reloaded. I doubt she or her trainers expected such a situation to occur, but she successfully cleared it and survived the fight. However, she needed that spare mag, and not because she ran out of ammo or broke the other one.
If you have a comfortable way to conceal extra mags and want to carry them - go for it... Better to have and not need as they say...
If it weren't for MA absurd laws, frankly, I'd go with Timber's technique and my car would be a virtual munitions dump
But unless you are going to have a truck following you with everything you could possibly need (including backup), you have to accept that life outside your fortress is always a gamble - you can incrementally improve your odds with training, firearms, knife, OC, asp, tazer, body armor, rifle trauma plates, quick-clot, bandages, etc...
I agree with you that if it's possible to carry spare mags (and if you can comfortably conceal them, a concern for most of us here) then you should. I was in a wedding a couple of weeks ago where my tux only allowed me to hide a small pistol, but no extra ammo. I didn't sweat it (probably because 3 other guys were carrying too
), but I had more nearby in the car, where they were more useful to me than they would've been if they were 1/2 hour away in the safe at home, although still less useful than they would be if they were on me.
I will concede there are many scenarios that I would prefer ammo and lots of it. I have carried extra mags in the past. Maybe if I had a comfortable set-up instead of a lose mag in my pocket I would be inclined to carry extra. But at this point I don't feel the compelling need to carry over what is in the gun. Of course life being life I'm now jinxing myself.
Beware of the ever possible jinx malfunction.
I'd recommend trying a few different mag pouches to see what works for you, but this can be frustrating, expensive and time consuming. You could try a spare mag in a cargo pocket, a pocket holster for the mag (I've never used one, but
someone on here sells them), or a belt slide or IWB spare mag pouch. There's a lot of options out there, but depending on your body style and manner of dress, some of them might not work for you. I actually have a friend who carries IWB and uses Thunderwear for extra mags, which also might be worth trying.
I'm also assuming that you live in Mass., which might make spare mags or ammo in the car not practical if you share a car with an unlicensed wife/GF or if your concerned about suitability if you lost it in a vehicle break in (long shot I know, but it wouldn't surprise me in some municipalities).
But ultimately I think more ammo is a good thing, so do with it what you will, and stay safe no matter what you choose to do.