One of the troubles with loading more than one ball, if using patch combinations that actually seal in the grooves, the air comressed between the balls has no where to go and will actually push the next ball back up the bore - as much as 4 to 10". That creates an obstruction for when the gun is fired - not a good situation.

I've tested double ball loads in 4 of my guns including the 20 bore, smoothbore - it was the worst for pushing the ball back up the bore due to the reduced friction of having no rifling. I had to use very thin cloth to allow the escape of the air between the balls. It wasn't fun to shoot at 640gr. per 'projectile' in a 7 1/2 pound flintlock.

My .14 bore English Style rifle, a caplock, will push the ball & ramrod back up off the powder about 8" if the hammer is not raised to 1/2 cock before seating the patched ball. A rough bore might not do that.

A single round ball of .490" or .495" will kill a black bear - easily. .40cal and .45 cal, much more popular in muzzleloading rifles than a .50 - back in the 1700's and early 1800's, killed black bears just fine. Even orders for rifles from the 'plains' in the 1800's were asking for rifles in the 80 to 40 balls to the pound calibres more often than not. These are equivalent to .38 to 48calibre. Rifles of .50 cal and above, were primarily for heavier game, like buffalo and elk in windy conditions and longer ranges.

The bullet shooting rifle makers, ie: inline makers would have you believe you cannot kill a large game animal with a single round ball. This is not the truth - their word is not trustworthy. They are in the business of selling bolt actioned rifles that are loaded from the muzzle, so technically, they can be called muzzleloading rifles. They have button rifled barrels of a form designed to be cheap to make with shallow rifling for shooting slugs, not round balls. The rifling twists are usually 28" to 32", again, not suitable, really, for shooting round balls. I have heard of some inline owners trying round balls for plinking to cut costs and actually get some practise without breaking the bank. The makers of these guns don't like this, as they'd rather you shot their expensive plastic jackets with expensive guilding metal jacketed bullets. They do not want you to shoot cheap round balls as they don't make any money if you do that.

80gr. of power is not a hunting load in a .50 - barely makes it as a 25yard plinking load. A .50 usually requires 110gr. to 120gr. of powder to deliver it's best accuracy with an oily or greased patch - in a round ball rifle, due to cut rifled, 48" or slower twist barrels. Water based lubes are not suitable for hunting as they WILL cause rusting. Oils and greases require/demand you use more powder to maintain accuracy. For example, both my .40 and.45 rifles demand an extra 10gr. of powder if I switch to an oiled patch from spit or other water based lube. My 14 bore rifle doesn't seem to care what lube is used as it shoots to the sights (regulates) with both water based and oil based lubes - identically.

In the early to mid 1800's on the Western Plains, it was said the .50 cal. round ball was fully capable for killing a grizzly bear. You merely shot him up through the open mouth.