I've been giving that some thought as well and I reckon that a stubby shaped nose, without the conical depression, just a flat nose ( a bit like the xxxx stubby with the lid on) and cast in hard lead, should give a similar performance.
A shape like this would easily come out of the mould halves.
The thing is, you don't want any expansion at all, the nose shape must stay as is for it to work.

I haven't made any boolit moulds for years, but I might just give this idea a go, just to see what the results are.