Actually that is a pretty good point about the staying power of the bullet. If the cops start blasting away and stray bullets are flying everywhere, it is better if it is a pistol round than hi powered rifle.
I seem to remember reading something similar when British police started being routinely armed at airports twenty years ago, there was much ado about the sight of policemen strolling around Heathrow with Heckler & Koch submachine guns (or assault rifles, I’m not a gun owner so I don’t know the exact description of the weapons).
Someone pointed out that in the wide open spaces of airport concourses with their marble and glass fixtures the cops would pose more of a threat than any terrorist if they opened fire with those weapons as the rounds would be sprayed everywhere and ricochet all over the place. What was required in such an environment was a pistol or revolver firing aimed single shots with soft point ammo (again I stress I’m no expert) to take out the bad guy(s) but the cops preferred the “macho” look of the H&K’s.
M4 — in .223/5.56mm — that is a “hi powered rifle”? Tell that to the M4 that lives with my 7.62s. 30-06s, and .300 magnums, willya...? That will up its self-esteem tremendously... ‘-{