I like 45 caliber pistols and revolvers. When I first got into my old trade, I greatly envied cop shops that authorized calibers like 41 and 44 Magnum, 45 ACP, and 45 Colt. A defensive pistol caliber whose decimal diameter starts with a '.4' is likely to be effective against ne'er-do-wells that conduct their depredations in an armed condition.
I am a big believer that bullet diameter is the caliber element most effective in halting exchanges of finality. Even illiterate mountain men in the fur trade era knew that a 36 caliber rifle was not as effective against 2- and 4-legged aggressors than was a .50"+ roundball. No roundball did a recipient much good at all, but the larger diameter sphere has been observed for several centuries to more reliably stop aggression, especially if a marginal hit is made.
We have all sorts of formulae that purport to predict 'Stopping power' of given bullets at given speeds. My favorite is Gen. Hatcher's Index Of Relative Stopping Power, or 'Hatcher Scale'. All of these formulae use a squaring of a ballistic element (bullet weight, velocity, or diameter) to arrive at their prediction.
I like Hatcher becuase it contains elements that hew more closely to real-world indicia than other calclations do.
1) It 'squares' the ballistic element (diameter)hat is demonstrably squared in the real world as the diameter is increased.
2) It uses 'mass' rather than static weight to express bullet weight--another nod to physics and reality.
3) It employs a 'Shape factor' to account for bullet form effects upon animated targets.
The data set for this IRSP is unlikely to be repeated again. As Gen. Hatcher alludes to in his texts, livestock ("beeves") was shot with pistol bullets to observe effects during the Thompson-LaGarde tests. The 45 ACP's design resulted from review of these tests--a .451" diameter 230 grain RN/FMJ bullet at 825-850 FPS. Another variable in the mix was our nation's experience in the Phillipines with the berserker Moro tribesmen. That lot of aggressors seemed less affected by the impact of the 38 Colt bullets than they were from the 45 Colt rounds that found their way across the Pacific. The 45 WORKED.
That message was heard by U.S. ordnance types, which is a remarkable event in history--desk-bound decision-makers actually acting decisively on the info provided by folks at the tip of the spear. What a sublime rarity.
My view--in the same way Gen. Patton called the M1 Garand rifle "The finest battle implement ever devised", I think LTC Cooper mirrored that sentiment in his promotion of the 45 ACP/1911A1 pistol as that rifle's first cousin. There were concerns early in my shop's autopistol adoption that the 45 ACP was difficult to master; it wasn't, even for non-enthusiast shooters.
"But the 45's speed means that it might not expand!" I loved that pogue-speak, that 230 WWB bullet expands well IME. My response? "It dARn sure won't SHRINK, either."
Sometimes I think we overthink this stuff a bit and imagination gets the better of us.