I don't think anyone plugs bores for hot bluing. Takes too much time in a production setup and would make a mess if one blows out. I never plug bores for rust bluing either.

Bluing, or powder stains?

Likely both, and as already noted, nothing 'I'd' be worried about.

Mining copper, on the other hand ...

Or fired cases not being able to be rechambered, if you rotate them 180 ...

A 7mm Rem, 200 year... garbage... sure looked nice ...

2 or 3 out of 5 no 3's, happily a 22 Hornet and a 223, no problem. The rest ... 'Problem'. 1 of them just needs stock work now.

Funny, I've owned, and still own, a lot of Ruger single shots and almost always solved any issues with load development (just like any number of other rifles). On the lighter barreled versions (NOT the heavy barreled varmint model), a piece of inner tube or similar between the barrel and fore-end tip can sometimes work wonders.
Some people like to put these fine rifles down, mostly because they don't understand them and have little desire to learn.

A case in point. This is a stock Ruger 1S 45-70 with C-weight 26" barrel and poor factory trigger (that I need to change at some point  )

yamoon wrote on Sep 7^th, 2024 at 10:35am:

Since Ruger started making their own hammer forged barrels in the early 1990s,  the QC and precision (aka accuracy) has increased. The conventional wisdom is that part of the earlier problem was the rapid turnout of barrels by Wilson to meet Ruger's demand, if not quality expectations.