Triggered by Lancaster's thread, I started wondering about the effect of those rifles on larger game.
The only ballistic figures I found were in the 1900 article by Preuss mentioned in the other thread:
a 24 bore (14.7 mm) cape gun used a ca. 22 gram cats head bullet behind 2.5 grams of black powder, giving a velocity of 265 m/s at 25 meters.

The 1877 book by Zimmer gives slightly stronger, but rather general loading recommendations:
caliber between 13.5 mm and 14.5 mm
bullet weight between 18 g and 25 g
powder charge between 3 g and 3.5 g
ratio powder to bullet between 1:6 and 1:7
Bullet velocity to be around 300 m/s.

I understand that in these days powder charges for breechloaders were about the same, certainly not more than for muzzleloading rifles.
I remember an old hunter's proverb:
Wenig Kraut und viel Lot schiesst weit und schiesst tot.
A little powder and much lead shoots far and shoots dead.

Now I am certainly not a magnum freak or the like, but at a red stag such loads seem anemic to me.
Still, the old European hunters managed to work with them.

Later BP cartridges used heavier bullets and much more powder and pushed their bullets beyond 400 m/s.
Also American muzzleloading plains rifles also were intended for lots of powder, for a powder to bullet ratio up to 1:2, resulting in really high velocity of the patched ball.
With such loads there is plenty of experience, they seem to work fine.

Can anybody tell about hunting with the old weak bore rifles?

Fuhrmann