Try Bas pro shops or Cabelas. They have a pretty good selection of recoil pads. Also a gunsmith can usually help you out.
Virtually the same.
Weight is what affects recoil. Cut the barrel, reduce the weight, recoil will increase if all else is equal.
Almost all- but the amount of recoil varies a lot. A .22 rifle has almost no recoil, a 12 gauge shotgun a lot.
A pump will have more recoil. The action of a semi-auto will absorb some of the recoil.
Similar to modern day shotgun
Generally, a gunsmith will fit a recoil pad to the shotgun using an oversized, standard pad. Not too difficult.
It is a shell for a shotgun that has less power than a standard shotshell, and produces less recoil, or "kick".
Recoil reduction.
It depends on the comparative charges of the ammunition. A rifle can have more recoil than a shotgun.
No
The modern shotgun will have a sharper recoil than the black powder. The recoil force will vary depending on the particular loading, but will tend to be heavier.
Numrich