I think there is a problem trying to make the .380 into something it's not.
I'll thumbnail this, because many here have heard it before. I've worked in some capacity on more than 200 handgun killing cases. After a while a pattern started to emerge, and it's stayed true. The only thing that will guarantee
the cessation of offensive action by a human is a hit to either 1) the brain/spinal cord or 2) the heart/aorta. An effective defensive handgun is one that allows the user to accurately target these vitals and provides sufficient penetration to hit them. That's all. Other hits might
stop a person, but these will
You might want expansion to increase the diameter of the tissue damage. Fine, so long as it doesn't trade off the penetration you need to reach
these vitals. You might want expansion to prevent overpenetration. Fine and noble - Rule 4 should always remain prominently in our heads.
Turning to the call of the question for this thread: Is the .380 cartridge underpowered?
I have worked now on dozens of killing cases in which .380s were used. I have never seen a case in which .380 hardball failed to penetrate to the depth needed to hit the heart/aorta or brain/spinal cord. .380 ball appears to be effective. (And, while I've worked on one case in which a .380 ball round overpenetrated its intended target and wounded a person beyond, it only hit the first guy's calf
so I have a hard time saying that it's a dangerously overpenetrative round.)
However, I have
worked on three shootings in which .380 hollow points
failed to penetrate sufficiently hit these vitals. (And these were fired from guns with longer barrels than the LCP types have.) Boy, but so many have been convinced that hollow points are the way to go (just look up-thread, for instance), and that's all the gun magazines show as defensive ammo from these guns. Not for me!
Think about what a hollow point does. By opening up and transmitting energy to the target medium, it loses the energy of its forward motion. The opening of a hollow point is like putting on the brakes, like opening a parachute.
It's exactly what you want/need when you're using something penetrative like a 9x19 in an urban setting, but is it a good idea for the slower/lighter .380? In my opinion, based on those three failures I've seen, no. A 115-gr 9x19 bullet traveling at 1150 fps is one thing; a 90-grain .380 bullet at 925 fps is another thing entirely. It can't afford to have the energy bled off - it may well not penetrate enough. Look at the gel tests out there. Do you have a .380 hollow point that meets FBI protocols for penetration from your gun? I doubt it. I would say that a .380 hollow point is not an effective defensive round.
But everyone should use whatever you determine is right for his own needs after doing his research.