Thompson Center in their early manuals for the Hawken had loads for double ball in .45 caliber for deer. After a while they discovered that it wasn't necessary, and it's poaching in many states to launch two projectiles in a single shot at deer during "primitive" or "muzzleloader season", and it's also considered buckshot in most states (even if fired from a rifled barrel) and some states also prohibit buckshot on deer, so they discontinued the data. Plus the problems if the second ball isn't properly seated on the first. :shocked2:
Of course where buckshot is legal one could use it during modern gun season, AND of course one could use it on coyote and groundhog.
My first question would be, Do you need it?
The idea was called "loaded for bear" because a lot more damage was needed on bear, and the term (iirc) stems from the post AWI era where Eastern rifles were trending in caliber to below the .50 caliber mark. Doubtful one needs it in a .50 and highly doubtful one would need it in a .54.
Now that's assuming you have a proper powder load behind the ball too. In an emergency survival situation, where one had say 1/2 the normal powder, perhaps 40 grains in a .54, it might be a good idea to ensure your deer was down as you had one and only one shot, and your shot was under 50 yards. I would hope that the extra 225 grains of lead wouldn't drop your MV so low that neither ball took good effect?
Basically it's a field expedient solution to increasing impact on large, dangerous game, from the days when all there was, was patched round ball. IF one was that worried about their load these days, one might try any one or several of the conical bullet designs on the market.
LD