This is a segment of a comment I made on TFB, preserved here because the argument comes up so damned often:
Those type of surface area calculations have virtually no value by themselves in a discussion of terminal effectiveness, so far as I can tell. I suspect they were popularized by Dr. Gary Roberts, who should stick to dentistry, I reckon. The fact is that these calibers do not generally speaking carve neat holes. Take a simple piece of evidence of this the "wound" created in a piece of paper by FMJRN .38" caliber pistol rounds, versus those of WC .38" caliber pistol rounds. Despite having the exact same frontal area, the displacement of paper is very different. If you do not know what I am talking about, there is a photo below illustrating it:
It's obvious that paper is not human tissue, of course, but the point is made. Bullets - wadcutters aside - don't cut neat chunks of flesh out of a target. They stretch and bend the tissue around them, including paper, which is fairly brittle in comparison to human fat, muscle, and other tissues. If this stretching is occurring, we would not expect to see very much difference at all between a .30" caliber "through and through" FMJ wound and a .22" caliber one, and indeed, we don't. In fact, doctors have a difficult time telling them apart, until the bullet is extracted. Indeed, look at the target again. The .38 and .45 wadcutter holes are easily differentiated, but the .38 and .45 FMJ holes much less so.
One should consider carefully the example above: The wadcutters carve the paper like a hole punch, while the FMJs stretch and bend the paper, making a much smaller, ragged hole. Given this, is it any wonder that the .38 Special semi-wadcutter bullet has a better reputation for terminal effect than other, comparable projectiles?