Great question.

This is just my opinion, but I use them on all my guns. My idea is this ....... that the way the strands in the tornado brush are looped, without any sharp ends to contact the bore, there will be no more likelihood of bore damage than with any
other style brush. I do not hesitate to use them on any of my vintage guns, and have never noticed any bore damage.

If there is evidence of bore damage from using them on vintage guns I would also be most appreciative to hear of it.

May God bless America and those who defend her.