As I understand it, Fusion bullets are manufactured by Speer, and marketed by Federal...both companies owned by same parent corp.
The process is proprietary, in which the jacket is applied to the lead core chemically, literally "one molecule at a time". This bonds the jacket to the core extremely well, making separation virtually impossible.
The other advantage in this is that thickness of the jacket is consistent, to within plus or minus .0003" or better. This factors into potential accuracy, as demonstrated by Sierra Matchkings which also run extremely close tolerances in this regard.
So far I've found Fusion ammo to be exceptionally accurate in my 25.06 and .300 WMs, as well as in several .300 WSMs with which I've had range experience.
In the bang for the buck dept., probably one of the best deals available for quality ammo.
IMHO and FWIW.