Well the pigs got that big sheet of cartlage (shield) behind their shoulder and thats gonna pretty much make any bullet expand fast like hitting the shoulder bone on deer. You might want to shoot a bonded bullet or maybe try the Barnes tripple shocks , or the old standard wich all great bullets are judged the Partition.
If it allows and you realy like the SST you can always shoot for the neck and head.
Most of the hogs we kill are problem animals and they are shot with a 22-250 and 52gr SMK's 99% of the shots are head shots but I have shot a few behind the shoulder and that little bullet does an impressive amout of damage to the lungs. But most of the time we catch them live cut them and feed them up with corn and grain to clean them out a bit befoe slaughter