crown damage?

[FOTIS]

CR-10 and sweets 762 works well for me also.

 

[ElmerThud]

For 30 years I've used bronze brushes/brass fittings to clean my rifles...never had a crown problem & no accuracy drop off, even in rifles I've owned & cleaned for 20 of those years.
Brass is much softer than the steel barrel & as long as the brush is pushed clear through the muzzle and careful withdrawing the rod, I really don't see a cause for concern...
Just my thoughts, Cheers