Trigger pullers frequently point out that a sidearm is something you only use when things have gone terribly wrong and you can't get to your rifle. Pistols suck they smugly say. They say there is no difference between 9mm and .45acp because inadequate is inadequate. They may even prefer the 9mm... because if its inadequate... you mas as well have lots of chances to make it work.
The problem with this of course... is it isn't true.
Let me demonstrate...
A 9mm (9x19 parabellum to be specific) is going to hit with say... 420 pounds of energy. That's for a 115 grain fmj.. and its being generous.
Now lets compare that to a .41 magnum wheel gun.
We'll give the 9mm pistol a capacity of say... 17. Fair enough? And we'll give the .41 magnum a perfectly modern capacity of 7.
17 to 7! Obviously the 9mm is the better choice right?
Well... a 170 grain bullet out of that .41 magnum is rolling out at over 1800 fps. That's more than 500 fps faster than what that pathetic little 9 is throwing that little 115 grain bullet. The .41 is producing over 1300 foot pounds of force.
So... looking at the 9mm... 17 shots X 420 pounds of energy... equals 7140 pounds of potential energy.
But 7 shots from the 41... at 1320 each... well that equals 9240 pounds of energy. 2,100 pounds more that the pathetic 9. In fact even at 21 rounds you're still around 1000 pounds less than what 7 shots of a .41 mag produces.
Something else to consider... people think of the 9mm as a small fast bullet. But please notice.. the .41 mag isn't just a much bigger bullet... its a much bigger bullet.. going much faster. Same with the .45acp. People thing its a big slow bullet. In reality a 185 grain bullet rolls out of a .45 at over 1200 fps... meaning its faster than a 124 grain 9mm. In terms of energy the .45 is hitting at over 600 pounds... so its no where close to the .41 mag above... but the ammo capacity is greater. 13 rounds in the case of a Springfield XD-M. So lets do the math again..
13 rounds times 616 foot pounds equals... 7969 pounds of potential energy. Again... several hundred pounds more potential energy available than the 9mm in spite of lower capacity.
Sure... if you have 21 paper targets threatening your life... I'm sure your 21 separate bullets will suffice to deal with it. You can punch a hole in each one of them.
In real life though you're more likely to face one or two... three at most attackers... and in that case... you better have a big hitter on your hip... not some glorified pellet gun.