To add a bit to Mike's post above;
Many longer sporting ( shot ) barrels were found to shoot low, so were bent up a little towards the muzzle to correct this tendency. (Some also had a built -in 'hump" at breech to counter low shooting)
If checked and not meddled with later, a good few long barrels, (Particularly over 50 " or so) will be found with this upward bend at the muzzle.
FWIW, a Getz 16 bore in my care needed such a tweak to bring the poi up to where I was looking.
All the best,
R.