I've got a completely off the wall suggestion. I know that it's a little unorthodox when the subject of Pitbulls comes up...but why not try to befriend the dog. If it was truly being aggressive, it would have attacked without hesitation.
I did that two years ago with an abandoned Pitbull, and she's turned out to be a loyal and devoted companion who won't even retaliate against my Chihuahua when he nails her in the face. I can literally put my hand into her mouth and take food away from her.
I should have been clearer. My recommendations were for head-shots only.the only reason that worked was because the 5th shot was a head shot.
A single headshot avoids the bouncing lead problem, and is better than a pointy stick.you can handle aggressive dogs neatly with a pointy stick, and you avoid bouncing lead all over the neighborhood.