ive hit an 770 with my left hand which i think was ok.

when i punch i always left punch first then follow through with my right which has more power, which is kinda hard to do on a machine where you can only hit it once!

my mate hit one of the ones thats always down except for when you hit it, was walking past and lamped it not realising no one had paid, thing stayed static, he fucked his hand up, we laughed!