Just read something elsewhere, and decided to ask. Apparently, the conventional wisdom is that if one is limited to FMJ, then bigger caliber is better. Is it true? The common knowledge is that modern JHP loads in various calibers aren't appreciably different in their effects on unobstructed targets, despite theoretical benefits of larger cavities with bigger calibers. What's then out there that perpetuates the advice of going with 45 if limited to ball ammo? Is it that 9 ball is below some arbitrary threshold, or over-penetrates too much, or just shown to be bad from the field reports? Or is that advice baseless?