If you love the gun, load her down to a comfortable, even if subsonic level, and see if it groups. Lob 'em in and have fun, but dont do too many at first, find what works for you. If you dont have one, check on those PAST recoil pads for your shoulder. All my friends who shoot 'big bores' have them.
Ive not had shoulder surgery, but have endured a whiplash type neck injury for years. When I shoot rifles of friends the black powder loads are MUCH better than smokeless, but even they get to me after only a very few shots. I went to the 38-55 TM, shoot smokeless cast bullet loads, and really like it.