I don't know about the strength like Fred has shown, but it doesn't really bother me too much. I use the criteria H&R has used since the very early 1950s on their various Topper models. The .22 Jet, .22 Hornet, .30-30, .357 Mag and .45-70 have been used on their cast iron frame (maybe the .44 Mag too?). The Hornet used to be a 47,000 cup loading and as such, was the highest pressure round out of the bunch.
I have a .357 Mag barrel on an H&R "AU" frame and a .45-70 on another SB1 frame.
It isn't a recommendation, it's just what I choose to do.