Why 3bet AK? Because you have read on villian's range and you're putting AK ahead of it. In the case of hh posted, mp pfr's. pf raising 6% in pokerstove gives us 88+,ATs+,KQs,AQo+ (which isn't necessarily his range but its a start given no other reads......given his shortstack, I'm dropping AT,AJ, AQ0) so we're behind 7 hands in his range, tying AK, and ahead of AQs/KQs. We probably shouldn't 3bet this hand