It depends.
It your ML pistol is an older style/design with deep rifling - Kuechenreuter, LePage, Charles Moore, Manton et al, then it was designed to shoot a patched ball - hence the deep rifling. This rifling is deliberately slow to rotate a comparatively light ball, rather than bullet of double the weight or more.
Some pistols of more modern design, like the CVA [based on the Hawken rifle] might be able to shoot such a projectile.
I've never encountered anybody shooting hollow-based conicals in an older style pistol. Shooting such a projectile in a modern design might be counter-productive, after all, what you are looking for here in UK is to be able to make a hole in a piece of paper with regularity, not, as we do over the way, shoot feral hogs.
tac