that is, a magnum 12 ga 1 oz slug, vs old style .45-70 load? 12ga is .72" diameter, 3x the frontal area of the .45. Essentially the same velocity. All you have to do is shoot a sealed 5 gallon can of water with each, or a few dogs with each, and you'll KNOW that the larger diameter slug has CONSIDERABLY more effect. Put a hp in that 12 ga, and MAN does it ever make a difference.
Which is WHY the 223, 70 gr Speer SP, even at 2600 fps and at 50m, does NOT have more effect on dogs, with chest hits, than does the 70 gr, 2300 fps 460 Rowland pistol load, (at 20 ft or so) because the .45 bullet has 4x the frontal area of the 223 bullet, and 2x the frontal area after the 223 sp expands as much as it's GOING to expand. Then there's the 3 separate wound tracks of the 3 segment Split Nose bullet, and the 3 overlapping temporary cavities, each one capable of damaging fragile chest organs, far beyond where the bullet segments actually make contact.
So those who CLAIM pistols CAN'T match rifle sp's in stopping power, I say BS. They CAN, IF you know what you are about when it comes to creating them.