"Grand Slam", "Game King", "Supreme", "Fail Safe" - you name them and they break up on big game.
My latest experience is with Winchester Supreme "Ballistic Silver Tip" and "Fail Safe" bullets. Like Nosler Partitions the "Fail Safe" breaks up in two to three pieces, some which go right through but the amount of meat damage is unacceptably gross on the opposite inside of the animal due to tumbling and the bullet's innards flying about.
The "Ballistic Silvertip" bullets behave identical to Nosler Ballistic tips - complete break up at the moment of entry with slivers of lead and copper deposited in the meat and huge exit holes on the light weight blesbok by the tumbling rear end. On big game at 30-06 impact velocity these bullets most probably will fail against the first resistance of shoulder and rib. Like the Nosler Ballistic Tip it is only good for brain shots.
On a young black wildebeest the 165gr Winchester "Fail Safe" broke up on the scapula and first rib and made two separate holes, each the size of a golf ball on the exit side. Most of the opposite scapula had to be thrown away. Clearly both pieces of the bullet had tumbled after break up. Inside the meat was a mess caused by smaller diverse pieces.
On a big blue wildebeest the exit damage caused by a number of "Fail Safe" bullets passing through the opposite side of the animal was a disappointing sight when the meat was processed. Because I am unfamiliar with the design I shall section a Winchester Fail Safe bullet and post photos here.
Winchester "Ballistic Silvertip" bullets were used on blesbok for body shots. Meat damage was severe - exactly the same as my experience is with Nosler Ballistic Tips, Speer Grand Slam and Sierra Game King at 30-06 and .308W impact velocities.