The 22LR and the 22Mag both run approx 24K PSI max chamber pressure.

Chambering & shooting the 22Mag down a 22LR spec bbl isn't something most factorys would do these days due to the dimension differences whatever small the difference, liability lawyers will just tell them not to.
Most every 22/22MAG conversion revolver uses a 22Mag dim bbl on the frame and supplied 2 separate cylinders to keep everyone happy.

In this case, the cyl gap will alleviate any pressure build-up as the very slightly oversize 22Mag bullet enters the .22LR sized bbl.

I really doubt it would make much difference in a closed system like a rifle as the Mag bullets though jacketed are so thinly encased that they quickly and easily swage down to the needed bore and groove size.
But that's just my opinion of course.

Anyway,,nice save on the cylinder and the revolver.
Someone probably got a bit carried away with a soft polishing fob and a Demel in those chambers.

Does (Popeye) Doyle sort & read the daily mail as well?