For the purpose of civilian self-defense with a handgun, let's say with a snub-nose revolver, does anyone see any practical difference between a bullet that expands and a bullet that "tumbles" -- assuming that both bullets penetrate into the FBI 12" - 18" standard?
To help focus the discussion, let's take a specific example. Here's a link to the Lucky Gunner web site and a ballistic gelatin test of Winchester Super-X 38 Special +P 158 Grain Lead Semi-Wadcutter HP ammunition :
https://www.luckygunner.com/38-speci...rounds#geltest
The ammunition was tested twice -- once from a 2-inch barrel revolver and once from a 4-inch barrel. There's a menu choice at the top of the page to pick which results you want to view.
If you look at results from the 4-inch barrel, you'll see that all five bullets expanded to about 0.50 caliber and all five bullets penetrated between 13" and 16" of ballistic gelatin.
Results from the 2-inch barrel show that none of the bullets expanded -- a total HP failure! Yet four of the five bullets flipped ends (tumbled, if you like) and penetrated the same 13" to 16" in the gel. The fifth bullet didn't expand or tumble and "over-penetrated" to 27" in the gel. We can disregard that "streaker" as having nothing to do with the question.
I'm guessing that there isn't any practical difference in self defense effectiveness between the bullets that expanded and those that tumbled. What do you think?