Jim. If you go to the Nosler web page and look up the failsafes you will see that they are not of conventional construction. They are copper with a steel insert in the heel and lead in that insert. This makes for a slug that behaves differently when it comes to pressures....compared to a conventional bullet.
For example where 76 gr of H4831 with a 180 NP is max in one of my 300 Win mags (3075 fps), if I use the Failsafe I can get the same performance at 72-73 grains of the aforementioned powder. Pressures are still the same (at that level) so this is NOT a carte blanche to keep on going up to 76 gr as you would with a BT or PT.