The greater the antimony content the larger the bullet. Antimony is one of the few metals that expand when cold and contract when hot. Linotype is rich in antimony for this reason.

The smaller the bullet is than the throat, the more it needs to be expanded by the gases to seal in the throat. The harder the bullet, the more pressure it takes to expand it. So you are in a Catch 22 situation. Reduce the Lino/antimony and make the bullet softer which might make is a little smaller, or shoot it harder and less likely to expand by the pressure.

I have noted the recent wave of thinking that says cast sixgun bullets must be the exact size of the cylinder throat and harder than a woodpecker's lips. However, I hold the opinion that a softer bullet is often better and will slug up to fit the throats.

It was common for older Smith and Wesson 44s to run .432 or .433 in the throats and they shot very will with .430 cast bullets, when cast soft enough to slug up with the pressure of the load.

pure will make the smallest bullet linotype the largest with ww inbetween. The tin in the linotype helps fillout and reduces shrinkage when the bullet cools.