You know I always wondered how the people directly behind that dude didn't get a bullet either. Indy could have shot right though the guy into an innocent bystander or two before the momentum of the bullet stopped.
Because not all bullets carry the same kinetic energy, or have the same terminal ballistics.
Google keywords to get you going:
YouTube ballistic gel test, FBI criteria, self-defense ammo comparison, overpenetration
I am a bit concerned about the general lack of basic firearm knowledge in today's society.
Just the same as if there was a lack about basic fire knowledge, or car knowledge.
Ignorance is not a valid survival strategy.
But assuming your question is merely from a lack of opportunity, not a lack of willingness to learn:
Even in 1940s, not all bullets carry sufficient kinetic energy to penetrate 6-12" of flesh or bone. Human or Game/Animal.
The bullet may yaw, squash, deform, fragment, tumble. And depending on bullet design intent: any may (or won't) happen.
Or even heavy clothing. A series of tests in 1980s ("FBI criteria") showed denim can "clog up" JHPs, hurting their function.
- Baseline "plated lead" projectile (Full Metal Jacket/Total Metal Jacket) are giant BB's, and flatten out like a snowball.
- More modern technologically advanced "expanding" (Jacketed HollowPoint) dump energy more quickly, thus penetrate less.
- Some even have a minimum velocity band to expand/fragment -- too fast, or too slow, and they don't work right.
(Eg: 5.56NATO is a "small caliber high velocity" cartridge -- can icepick, fragment, or expand -- depending on ammo design.)
Small caliber handgun revolver cartridges like 38SPECIAL (as in Indiana Jones) from the 1940s generally were the former.
A FMJ 38SPL might penetrate if you hit an arm or other "thin" profile. Or might not if you hit center mass torso or bone.
There's a lot of engineering behind projectile design and "terminal ballistics".
And lot of fearmongering too. Causing concerns like yours from normal people who don't know deeper.
Sometimes it weedles it way into laws, which is super annoying. Or manga art, which super-duper triggers people like me.