Been years ago now, but IIRC for this or another thread, I did an experiment to compare effort needed to draw/resize:

1) mono bullets
2) copper/gilding-jacketed lead-core bullets
3) Hornady steel-jacketed lead-core FMJ's

All in .375 cal using a variety of dies I've used to reduce to .366-.369 caliber. The gilding jacketed lead-core jobs are rather easily re-sized, as Daryl and I have been doing for many years now {re-sizing .375 lead-core bullets for use in 9.3 rifles}. The monos are almost all impossible to reduce and the steel-jacketed lead-core FMJ's were an absolute no-go, presenting an absolute stop to attempts to resize them using the same equipment used to draw the lead-core jobs.

In my mind, if the monos actually are capable of damaging a rifle bore, the FMJ's would absolutely wreck it in a few shots, depending on all the standard variables, of course {bore/groove diameter vis a vis bullet diameter, etc.} I have no experience {I don't think, it's been years...} with "extra stiff" Woodleigh steel jacketed bullets, but if they are anything like the Horny's I tried, would be no-go's with my equipment as well, and maybe even worse.

To me this entire issue involving OSR remains a mystery.

PS: There was one one mono bullet I could resize that had multiple, very narrow driving bands. Took effort, but could be done. Can't remember which it was. Been so long.....