A friend found this in some old milsup bullets he had, and doesn't know anything about it. Anyone recognize it, or have any history?? I have seen something similar with really old 303 British from the 30's and 40's, when they used a heavy crimp down the neck instead of the case mouth, but this one is a .308.

Could just be low quality war time production when they essentially released anything that would go bang. You should read about the quality control on the hand cut WW2 grenade fuses some time.

That is a Herters,( Waseca Minn.) Wasp Waist Sonic Bullet. I use to see those in the '60s. I hope this helps.

That looks like Jane Mansfield’s measurements. 36/24/36

Thanks Kell, that looks like a winner!

"Only if she five three"

That does ring a bell. I don't recall what the theory was behind the design, though.

If nothing else it would reduce bearing surface

They were trying to take advantage of a section of aerodynamic Theory called the area rule that helps stability in the transonic range. I think it's very unlikely that it would work on something so small but I have very little experience with aerodynamics at supersonic speeds outside of simply playing with math problems.