Recoil shouldn't be a concern under 50 caliber, even with injury. 40 gives you more options, but is also "too small" for big game in many, if not most, jurisdictions. Here in TN we can go as low as 36 for deer by statute and I've seen a 40 do a fine job--but you didn't say anything about hunting. Just don't get hung up on 32 as being much lighter in recoil than a 40, and many old timers report that handling 32 caliber balls in cool weather can be challenging.
I'd try to find something I liked second-hand but also checked out thoroughly by someone who KNOWS black powder and what to look for in a used gun. Most modern gun shops will not have a clue, and should be avoided without good references otherwise.
I don't know what there is on the production gun market, haven't looked in ages. But I do know for a few dollars more, there can be some great options.
Could be some knowledgeable members in your area. I'd try to make contact with them, see how they think. Post your whereabouts maybe.
