I could see hollow pointing a ball might work. Back in 86/7 when first shooting the .69, I was perplexed about the .682" balls flapping the strings without cutting them, thus I used to cast
5/8ths to 3/4's balls for the string cut on our trail walk. These worked (I think), but, well memory fails me and I don't cast those any more. If the string (butcher's cord) is hit with the centre of
the ball, it gets cut.
Don't know for how far, these flat nosed would shoot before becoming unstable. Since they are much lighter than a normal ball, they would follow a different trajectory.
The same would be for a drilled hollow point - getting the hollow point exactly centered in the bore might be difficult without a "pegged guide starter" made specifically for this.
As we all know, pure lead balls expand beautifully on their own & we are usually talking about modifying (hardening) them to get deeper penetration through less expansion, than the
reverse scenario.
Too- the other factor that comes into this, is pure lead, which most of us use for our round balls, does not tend to fragment, like harder alloys do. Instead of fragmenting, pure lead balls
expand & stick together in a solid lump, as if made of bubble gum. They will flatten out like a pancake, though, given enough resistance. Taylor's Brown Bess moose ball did exactly that
to be found under the hide on the off side. The initial velocity was 1,200fps driven by 100gr. of GOEX 2F - we chronographed it - back around 1980.