If the bullet stops within the target, then all its energy has been deposited. That's not to say that an FMJ can do as much soft tissue damage as an expanding bullet... but I'm not an expert in this field.
If you use Power Factor calcs, a .45ACP bullet has a lot more energy than a .223 (I'm assuming 950 fps/230 gr. and 2300 fps/55 gr. respectively.)
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