The problem with someone's comparisons is they depend on too many factors which just aren't going to happen all that often.
1.) The .223 is going to be shot through a glorified pistol barrel, and be overloaded to the point of blowing the primers out, if you even manage to compress the powder charge advocated far enough to seat the bullet.
2.) The preferred sidearm will somehow hold together after being chambered for a dead cartridge, and assuming the aforementioned someone will make his own bullets and load his own ammo, and 'smith the gun. . . .all federal felonies for him to perform, when this same person is too afraid to get a travel waiver to go camping.
MODERATORS: I point this out only to show that the "magical" guns with the "magical" bullets won't be there in real life.
3.) None of his engagements will be outside of 90m, the effective range of his dream bullets, or outside of 45m, the effective range of the much vaunted "GI round".
(NOTE: he won't be using 80-gr. VLDs because he MUST have the ability to spray 'n' pray to make up for lack of ability with a rifle, and 80-gr. VLDs won't feed from the magazine, so he'd be effectively making his fantasy gun a single shot.
4.) .308 users will only be shooting non-fragmenting FMJ loads. Never any of the fragmenting FMJ, FMJHP, ballistic tip, Failsafe, etc.
5.) .45 ACP users will only be shooting FMJ, not any of the premium, highly effective hollowpoints out there. This same assumption is made for all other calibers carried, the users MUST be carrying the LEAST effective ammo for his dreams to have any merit.