The ballistics of the venerable 30-30 aren't much different than the 7.62x39. Great medium range round. Get an AK or SKS. Cheap, fun.
I think I personally would choose a model 94 but did not mention it because he was asking about semi-autos. I would also have a Williams or Redfield receiver sight with the standard front one.
Model 94s are so easy to carry and in a fight you can shoot one then load one from loose cartridges in your pockets etc. That way you can always keep a full mag ready.
A model 92 in either .44 or .357 mag might be an even better choice.