sorry if this seems like a dumb question, and i'm sure the answer is probably going to be something obvious, but it's been bugging me.

according to fackler's wound ballistics theroy, temporary cavitation doesn't matter, and the important factors are sufficient penetration to reach vitals + permanent crush cavity.

so, if temporary cavity is not important, what is fackler's reasoning for why .308 FMJ does more damage than .45acp FMJ?  both rounds have enough penetration to go right through the average person - and .45 acp will have a larger permanent crush cavity volume due to it's larger diameter.  I realize that .308 will probably yaw at some point, but yawing is fairly brief and doesn't crush that large of a volume of flesh.  so what's the deal here?  i can't help but think that temporary cavitation is a more important wounding mechanism than fackler is letting on, but i'm sure he has an explanation for this - i just can't find it.

according to fackler's wound ballistics theroy, temporary cavitation doesn't matter

Common handgun bullets do not produce a temporary cavity large enough to reliably damage soft tissues.  Most energetic handgun bullets produce a temporary cavity no larger than about 4" in diameter, which can be tolerated by many tissues.  This is the basis of Fackler's claim.

.308, on the other hand, when it yaws, produces a temporary cavity about the diameter approximately the size of volleyball, which cannot be tolerated by even the most resilient of soft tissues.

The 308, is generating the hydro-static shock which delivers a larger amount of trauma to a larger amount  body.  I believe 308 travels around 2600 FPS.  Handguns which can generate enough energy to penitrate through the body, do not generate enough energy to create the hydro-static shock.  

Taggage.

Fossil_Fuel, this is a very good question and I hope nobody comes by and just says "Read the ammo oracle" or some pat answer because I've read it stem to stern (as well as a lot of great articles/posts by DocGKR at TF) and it doesn't explain this.

Likely it is a difference in wound mechanisms (a somewhat tumbling .308 + hydrostatic tissue damage = higher % of killing wounds) but do NOT quote me on that.

The permanent cavity of the yawing .308 round will be quite a big bigger than the permanent cavity of a .45 caliber hole all the way through. The effectiveness of non-fragmenting, non-expanding FMJ 7.62x51 is dependent on yawing. The couple of inches of "yaw-time" are traumatic enough to most tissues.

The question I have is: does non-fragmenting, non-expanding M80 ball make a bigger PERMANENT crush cavity than a properly fragmenting 5.56x45 ball round? According to Fackler's pictures the smaller, fragmenting round wins over the bigger one, despite the big differences in bullet size and energy.

The temporary stretch cavity ceates wounds similar to bruising unless you hit a non elastic oragan like the liver or brain or even astomach or bladder full of water where it causes massive tissue disruption and tears the tissue apart or pushes the water to the point of rupturing the organ containing it.  Handgun bullets do not have a very large or strong temporary cavity wounding mechanism.  Also as mentioned the .308 yaws and certain .308s like the old West German will fragment.