I am not a fan of bronze brushes at all. Unfortunately, I don't have the ability to take pictures with my good scope (it's a rigid, 17" Olympus I found at a swap meet for cheap because there was no light source... I cobbled together a Mini-Mag light and it works just fine). I have a cheapo scope but it's not as clear, but i made one pass down a relatively clean custom barrel w/bronze brush and could see fine scratches in the mostly mirror finish of the bore. I still use them in pistols that shoot lead bullets but they never see my rifles, even my AK & SKS just get nylon now.
I am also not a fan of bore snakes as they get totally filthy after the first couple of passes and now you're pulling a crud infested item thru your barrel. Generally powder residue isn't too bad but the stuff from primers and bits of carbon can be very bad for a good bore. At best you can wash them in a washing machine (do NOT let your wife or SO see this happen) after each use. Like patches, tgey should only go one way thru the bore.
I suppose that in most factory barrels you'll never notice a thing but I have some customs with hand lapped barrels and I'm not doing anything to jeopardise their finishes. The same goes for any type of scrubber pad (Scotch-Brite). I wouldn't even use the white ones, which have the finest grit of any of them! The airline I worked at used to use them (with a polish) to put a super brite finish on bare aluminum. I will admit to being a bit anal with my barrels but I have some that are great shooters and I don't want to do anything
that might affect them adversely in any way!
Again, with todays available chemicals there is seldom, if ever, a need to "scrub" a barrel! Probably the worst thing I've ever seen for barrels was a stainless steel brush! Yikes! I don't believe anyone even makes them any more... which is a good thing!
So... Always use a bore guide (I've even made some for pistol barrels), use quality products, use lot's of patches going 1 way thru your barrel (I cut up paper towels for patches... the only thing that requires a cloth patch is JB pastes) and give your barrels the best possible chance of shooting their very best for you for as long as possible!
PS. Go here for the Scotch-Brite color code: