Plus, one of the reasons the FBI liked the 10mm is the ability to load it up or load it down.

Moreover, it had the potential to penetrate deeper -- while expanding to a desirable mushroom -- than a .45 or a 9mm. (Of course, that depends on the loading. One problem with full metal jacketed 9mms is their tendency to whizz straight through targets...So penetration isn't the only factor.)

Even the attentuated 10mm round the FBI "labs" were testing would have reached the heart of one suspect in the "Miami Massacre".

Still, what the FBI needed in that -- and any similar situation -- was the right rifle with the right load -- with a good 10mm as a BACKUP -- not a PRIMARY -- weapon.

Pistols are great -- but, people, there's a REASON THEY'RE CALLED "SIDEARMS"....

Pistols are BACKUP WEAPONRY....