Barrel lengths were 3 - 4" any difference from that won't make much difference. What does muzzle energy matter? Secondary fragmentation? Marshall & Sanow (and Ayoob has helped propagate this stuff) have really made a mess of self defense rounds and have never risen to any of the challenges others in their field have presented to them (I wonder why?). The 125 works very well as long as it gets there, which it occasionally hasn't done. Look, people's reactions to being shot are completely unpredictable; stopping power, energy dump, one shot stops etc is just nonsense. A State Trooper here was hit with a 32ACP and never fought back. A perp took (2) 12GA slugs the chest and ran away from the scene before expiring - he chose to flee; he could have fought instead! (I'll give Ayoob credit for one thing in LFI 1, he works long and hard to show his students how all of these rounds have failed to "stop" in the street) All we can do is choose a round that is reliable in our weapon and gives us penetration in a reasonable range - I'll leave that definition up to you but the current FBI requirements seem good to me. That leaves loads like the 125 Federal out in the cold. Use them if you like - I'll pass. I'm not trying to put anyone down here, I just don't want people out there walking around with unrealistic expectations.