Hello and thank you for coming to Just Answer. We appreciate the opportunity to help you with your firearms questions. If I define "powerful" as the muzzle energy in foot-pounds, the three most powerful semi-auto handgun loads are the 357 Sig, the 9X23 Winchester, and the 10 mm. There are other ways of defining power, such as velocity or stopping power, but according to the manufacturers' specifications these loads have the highest muzzle energy.

I hope this answers your question. If you would like me to look at cartridges using other definitions of "power" or if you would like more clarification of my answer, please let me know and I will be happy to continue to help you.

Thank you for the compliment. I'm glad that you are happy with my service. I've actually been working with Just Answer for a few years in the Tax category. I've only started answering questions in the Firearms category recently.

It's difficult to rank the energy of the three calibers, since each manufacturer lists a slightly different muzzle energy. The 357 Sig varies from 414 - 525 ft-lbs; the 9X23 Winchester has only two manufacturers at 583 and 587 ft-lbs; and the 10 mm ranges from 425 - 605 ft-lbs.

I can't find any official measurements of terminal ballistics. Generally, a hollow-point or a soft-nosed bullet will maximize your terminal ballistics ("stopping power").

If it helps, the 357 Sig varies from 257 - 375 ft-lbs at 100 yards; the 9X23 Winchester has one listing of 338 at 100 yards; and the 10 mm varies from 310 - 418 ft-lbs at 100 yards. That should give you some idea of the energy drop-off over distance.

I hope this helps. Please let me know if I can provide more information on this question.