A Question for You Cast Bullet Guys.

I'm using Mt. Baldy Bullets' .452" 270-SAA bullet in my .45LC loads and it has an advertised Brinell hardness of 11-12. Now, I know that hard-cast bullets and heat-treated bullets with hardnesses of 18 or more won't expand, but with a hardness of a relatively soft 12, would this bullet expand in ballistic gelatin at velocities of 900fps or so?