I have not tried them at 4000fps
but i have tried them at 3400fps on rabbits,
they were a bit dissapointing, the killed them ok but very little expantion,
i think its due to not enough body mass for the bullet to expand in before it passes through.
The exit holes were only about 1" cretainly nothing like a 50 Vmax or 52 Amax
If you run them at 4000 you might find they expand better ??
john