I think the SST bullet in general has been redesigned and the jacket was made thicker on them.The same thing was done to Nosler Ballistic Tips.Earlier versions had thinner jackets and were very explosive.

~Molɔ̀ːn Labé Skýla~
As Bob Hagel would say"You should not use a rifle that will kill an animal when everything goes right; you should use one that will do the job when everything goes wrong."Good words of wisdom...............