Thank you flat top. What I was specifically wondering about was softening the nose of my beartooth bullets to produce a larger wound channel on shot game. My thought is that by softening only a portion of the bullet it will mushroom better but retain enough weight to drive deep. I wonder will it work? and after reading your post I wonder will the softened area stay soft for an entire hunting season? Has anyone tested anything like this?
Joe, the fact is, they do expand, depending on hardness. This is the thing, lead alloys do not have the tensile strength of copper. That's obvious, but what has taken me a while to realize is that the cast bullets with soft to medium-hard alloys do expand. They expand similarly to jacketed bullets, then the outside area of the mushroom shears off without the jacket to hold or support the lead alloy.
So, get a load of this. Cast bullets are giving you the benefits of the expanding bullet. The benefits of a rapidly expanding bullet are recognized quickly in terms of the full set of terminal events from impact to the point that the bullet comes to rest. With most expanding bullets, the point from impact, expansion to rest is very short. With cast bullets, of medium to medium-hard aloy, the bullet's nose expands and gets the benefits of the expanding bullet, but when the edges of the mushroom sheer away, it leaves the bullet with a pimple tip that makes for a good profile for penetration. So you get the big initial energy transfer and deep penetration.
With, say 30 cal bullets, what makes them expand so rapidly is 1)high impact velocities 2)pure lead or a soft ally used in those jacketed bullets. With cast bullets, we can use a meplat size to speed up or slow down that initial energy transfer. When the alloys get harder, expansion is less and nose tends to shatter as opposed to mushroom and shear. Don't underestimate the terminal effects of those parts shearing off as they can be as heavy as a 22 bullet.
This is the Safari Grade with a soft alloy. Look at those pieces that I re-assembled to show what the bullet looked like at one point in the early events of it's terminal performance. The softer alloys will sheer to away the outside edges of the mushroom, but as the alloys get harder, more of the nose breaks away with the mushroom.
Here is the Lead Head with the piece of sheared mushroom. Alloy is harder than the bullet above, so more of the nose sheared away.
This pic is what that Lead Head looked like going from 4th jug into 5th jug. Understand this is midway-point of some serious total penetration. That's the 2 foot point. Basically a fist sized exit hole on a broadside elk.
This pic represents two different ranges of impact velocity. In each velocity range, there is a bullet that is water quenched (about 27 bhn) and air cooled wheel weight bullet (about 14bhn). The WQ bullets are on the left side in each set and the air cooled on the right.