.357 Sig vs 9mm bullet construction vs. 9mm carbines

[OlongJohnson]

This post is purely ballistic/dental geekery on my part, as I have no personal desire to own either a 9mm carbine or anything in .357 Sig. However, as a mechanical engineer, I enjoy understanding details of technology.

One of the downsides of a semi-auto pistol caliber carbine, in my mind, is that the bullets end up being driven significantly faster than their designed speed range, which can have negative consequences for the terminal ballistics if hollow points are used. Over expansion, reduced penetration, breaking up, unpredictable interaction with textile layers, etc. (Of course, that depends on the specific bullet design and its interaction with the specific target, and is subject to round-to-round variation.) In essence, it means the carbine is in theory more effective as a range extender than as a "power"/effectiveness multiplier for conventional defensive ammo.

I've noticed .357 Sig bullets in almost the same weight (125 gr) as similar 9mm bullets (124 gr), but am having trouble finding definitive descriptions or explanations of the differences. It's logical that the .357 Sig bullets would be constructed to have proper terminal performance at the higher velocities of the bigger cartridge. I've googled the heck out of it, and have found some discussion to that effect, but then when people inspect examples of factory-loaded ammo for both cartridges, the theories often don't appear to match observation in the environment of very incomplete information.

Obvious potential differences:
-thicker jackets
-differently shaped HP cavities
. -shallower
. -smaller diameter (which would mean different ogive as well)
-tendency to invest in bonded technology
-lead alloy characteristics (hardness/toughness)

Theoretically, loading 9mm ammo intended to be used with a longer barrel at higher velocity with projectiles engineered to work optimally at the higher velocity associated with .357 Sig would be a better mousetrap.

Just wondering if any SMEs have actual product knowledge in this area and could share with the group.