Heh, heh - you're thinking of speeds I hadn't considered.

12 balls, 4 layers would give just about 1,600gr. weight, about the same as a single 4 1/2 bore ball would, for a muzzleloader.

Of course, the rifle's action will allow more pressure, higher velocity - and a paper wrap or two around the balls, ie: post-it note paper from a pad might help hold them together a bit longer for better patterns.

Interesting concept.