PC allows you to get away with softer alloys up to a point.
I'm betting Popper is playing closer to the 24-2700 fps zone though.
It don't work the way you think it does.
I did a bunch of tests just like yours and the quench sucked the heat out of the noses so fast they actually got harder than the bases. What happens is the heat is sucked from the nose into the base and then into the water, and the base stays hot longer, making it in effect cool slower than the nose. Hence harder noses. The longer and more pointy the bullet, the worse the effect.
weird that's how brass annealing works too.
you'd think some smart guy would write up some kind of physics paper and name it [insert name here]'s law.