"The bullet through Platt's upper arm caused considerable damage. Besides rupturing the brachial blood vessels, there must have been significant nerve injury since several of the major nerves of the arm travel with the brachial vessels. However, at least a portion of the median nerve, which controls the muscle used to pull a trigger, had to have remained intact since Platt did continue firing his Mini-14. The large ragged exit wound from the arm and the jagged entry wound into the chest suggest a tumbling of the bullet as it entered the chest, passed through the fifth intercostal space, and stopped in the hilium (perhaps damaging either the pulmonary artery or vein or both.) A markedly deformed bullet can be seen in the hilar region in the chest X-ray (Fig. II-4). The right lung was totally collapsed and the right pleural space contained 1,300 ml of blood - a major life-threatening blood loss. Blood actively exited from the brachial vessels as evidenced by the large quantity of blood that Platt left in his wake and on Grogan/Dove's car (Plates II-C, D, E) as he moved around the car's right rear, then the rear, then the left rear, while shooting Hanlon and then Dove. No other vascular injury sustained by Platt was of sufficient magniitude to deposit the large quantity of blood found at the scene. Platt Wound B was probably a non-survivable injury."
--W. French Anderson, M.D. on the Miami FBI Firefight, 11 April 1986
The aforementioned wounds were caused by the "puny" 115-grain Winchester Silvertip bullet fired by Agent Dove. While the round did not stop Mr. Platt's ability to keep fighting, it could be argued that he should have been incapacitated. Other people in other circumstances probably would have been. Mr. Matix, Platt's partner, took a devastating headshot, yet for from one to two minutes he was able both to analyze situations and to move with purpose around the scene. He should have fallen down dead, but he didn't.
If any specific factor was to blame for the firefight not ending sooner, it could be that while "most" felons hold out hope of surviving, neither Platt nor Matix was particularly interested in going to prison, so they fought with a fatalistic ferocity few could muster. When you add a huge dose of adrenaline to an uncompromising decision not to be taken alive, it's likely that anything is possible.
Current 9mm carrying ammo for me is the 125-grain Cor Bon or the 124-grain standard Federal Hydra Shok; both were chosen for the extra penetration they offer, combined with good expansion to keep them in the target. An extra inch of penetration might very well have put Mr. Platt down for the count with that first solid hit. Or maybe not, but I prefer a bit more of an edge.