This was also presented in O Sensei's biography, The Invincible Warrior. While enjoyable to hear, I wonder how much of this was propaganda? Gozo sensei is a biased source for this information after being a uchi desa for O Sensei. I'm not saying this didn't happen, but I would like to see some other accounts of this occurance. Too bad there probaly are not any.
I think in the book it was rifles and not pistols? It's been a while since I have read this.. Concievably, if flintlocks were used, there is ALOT of smoke due to the amount of powder being burned off along with a flame from the cap ingniting the powder.. a good 1~3 seconds before the ball is actually fired. I could see one with years of martial experience being able to dodge this.
Thinking about the feasability of this and how in the context, Osensei says, "The golden flash has a spectacular noise,"... I think this was done with some form of flintlock or non-capped cartridges.
There is also the possibility that O'sensei could read the body language of the shooters and knew who would be firing at act accordingly, or he could read their minds, or perhaps they were afraid to shoot at him and missed on purpose.
No one will ever know for sure, so we take in stride. I know will not be trying to dodge bullets anytime soon. Of course, when the time is right.. I won't have to!