Bob - first glance at the first recovered bullet made me think of an expanded round ball of alloy slightly softer than WW. I have one from my 14 bore that looks almost identical, but it took out a concrete block about 4" thick X 10" X 12" - nothing but chunks less than 3" in size. That was the first power lesson I had with that 'medium/large' bore rifle.

Your bullet, actually being pure lead, shows how amazing pure lead is, in holding together when it should have broken up long ago. Like Bubblegum, it is.

Nice narrow lands and wide grooves in that rifle. Cuts down on pressure, improves speed and cleans up the easiest of all shapes except maybe "Invisible" rifling.

If you have straight WW alloy available I'd try one just for comparrison. That might give you a good penetrating soft.

Lyman #2 alloy is supposed to be around brinel 16 as cast, while WW is in the 10 to 13 range, as cast, making it slightly more ductile than #2, less prone to fractures and chunks breaking off.

Further hardening of a higher antimony alloy might not be as good an idea as first seems, and might not be necessary, either. With higher antimony as in the #2 alloy over say, WW, further hardening will cause a brittle nature, sluffing of material. That may or may not be what you want, I don't know. The retained weight is still pretty good, but bones might cause more weight loss and less penetration overall.

More experimenting - WHAT FUN!!

As you probably understand by now, I really get a charge out of testing variations.

I-too think a RB would work well - of course HA!.

A hardened straight WW ball or bullet will be more ductile, less brittle than one with higher antimony in it, even though they are of the same hardness.

I'm trying to remember back about the 340gr. hardened WW alloy .45 calibre pistol bullets Ross Seyfreid shot the Cape Buffalo with. No breakup and penetration like solids IIRC.

It all comes down to more testing, more shooting.