Does two different alloys at the same bhn expand the same?

[outdoorfan]

In a solid-nosed configuration (no HP's). For example, would ww/soft at 50/50 at 9 bhn have the same rate of expansion as 25-1 at the same bhn? Or, would the 25-1 expand more due to not having any antimony. I haven't tested this in my .45 Colt, but I've been wanting to. Anyone done this and have observations?

[Doc Highwall]

No. Because the tin is more ductile then antimony.

[Bass Ackward]

This is a trick question.

BHN is BHN. So 5 different bullets fired exactly the same with identical meplat widths, strike velocities into the same densities so that they experience the same shear forces will begin to expand at exactly the same point / time. Doesn't matter what's in them or how they got to a certain hardness. Forces to begin expansion are equal.

But once they begin to expand, then everything will be different. Expansion of lead tin will fold easier with a tendency to round off "more uniformly". And it is less likely to break up.

An antimony mix of identical hardness will be stiffer and less flexible so it will expand wider making it more likely to break up before it completes the rounding process.

Think of it sort of as painting with a new brush vs one that was used before and not cleaned properly.