shouldnt hurt it anymore than it hurts steel.
i personally dont like that stuff as i dont believe there is any real need to remove every trace of copper out of a bore after every firing session. after 30 or 40 thousand rounds maybe it would be time for a good decoppering but as a routine cleaning thing i dont think its needed.
if your shooting bench rest with a rifle maybe but thats a special case.
im moving this over to the cleaning and maintenance subforum you might get other opinions there.
"Gun control: The theory that a woman found dead in an alley, raped and strangled with her panty hose, is somehow morally superior to a woman explaining to police how her attacker got that fatal bullet wound." — L. Neil Smith
The problem with being stupid is you cannot simply decide to stop doing dumb things...
"I crapped my pants to avoid the draft!!" -Ted Nugent