In all my games, no T70 has survived more than 2 shots, the first one dealing more than 50% damage.
Perhaps a lvl T70 can survive 3, I don't know for sure.
its all dependent on rng. on the first shot will always take half its hp. the 2nd shot will always take it down to 0 hp. however, death is considered a crit in this game. a t70 has an 80% chance to die when its at 0 hp (that includes a 5% chance to be abandoned). theres a 10% chance it will lose its enginge and a 10% chance its gun will be destroyed.
the situation imagelessbean described only happens very rarely. for a t70 to survive the 2nd shot, it either lost its engine/gun or it wasnt a direct hit. the scatter can hit near the t70 and cause it to deal slightly less than 160 damage. the chances of either of these is obviously quite slim.
https://docs.google.com/spreadsheet/ccc?key=0ApmrrrPr20ncdEpuSHcxNko1VGVFYjczYXpFZWhqOHc&usp=drive_web#gid=11