Like Daman said, TSS has a density of 18 gm/cc compared to 12 gm/cc for the HS in H13 and Nitro Ray's standard (not Mega-Weight) HS loads. That allows you to shoot smaller shot than you could with HS. Patterns with TSS 9s are amazing and will kill a turkey really, really, really dead at 40 yds.
But it is a handload only proposition.