OldMarksman
Staff
As military rifled muskets changed from 15.4 mm 11mm to 8mm or 7mm, and from 69 caliber to 50 caliber to 45 caliber to 30 caliber or .303, one of the benefits was flatter trajectory and consequently, a longer effective range.Since the invention of firearms, military and big game weapons have always been large bore weapons, the smaller stuff just didn't cut it when defending yourselves. Small caliber guns came about for the ease of carrying, not because they were more powerful, they were also easier for frailer people too handle. But as far as shot for shot, I believe that the bigger calibers are more effective.
That meant that "shot for shot", the smaller bores were more effective.
Of course, lighter ammunition was important.
For big game, there have been differences of opinion, as exemplified by Newton and Weatherby on one side and Keith on the other.
Of course, one would quesion the wisdom of anyone who took a .50-110 on a one-shot antelope hunt.
But none of that is relevant to the subject at hand. In a self defense shooting against a human attacker, "shot for shot" effectiveness merely has to be good enough. The unwanted side effects of having more are not helpful at all and will work to the defender's disadvantage.