Wow. I'm glad to see I'm not just weak. I fire my milsurp rifles with no flinch, including the Soviet M44s; however, my little single shot H&R/NEF .410 leaves me with a worse sore shoulder than any of my rifles ever does.
Mine is a Tamer with a synthetic stock, so it's pretty light. It's also the thumbhole style stock with shell storage, so the length of pull is a bit short for my long arms. I may replace the stock with a regular-style synthetic stock. That means giving up the in-stock shell storage, but it's worth it if I can shoulder the weapon better and hopefully reduce the punishment I'm getting from recoil. Other than the fact that it kicks a bit, I've never had a problem with my H&R single shot. Once a shell didn't eject until I rammed it out with a dowel, but I think that was the ammo, not the shotgun. It has never done that to me again, and I've fired several hundred shells since that one.