is it safe to use shooters choice copper remover on non chrome lined barrels? Do you have to use this every time you fire weapon, or cleaning session or only after every few thousand rounds only? Will it damage the brush of my OTIS kit? because it says in the instruction not to use phospor bronze brushes, what are OTIS brush made out of?

yes its safe as long as you follow the directions.

if the brush has like a copper color to it its a bronze brush, using t5his brush with copper remover any copper remover it will attack the brush and the copper in the barrel, you will get a false reading as to just how much copper is in the barrel. The brush will not last as long. I still use them I just wsh them off with brake cleaner when i am done. I use a plastic loop to apply  the copper remover and let it soak in the barrrel for no more than 10 mins.

My varmit rig a rem vssf in 308 i use the copper remover every 100 rounds or less. Your groups will tell you when its time to use the stuff. that and looking down the bore you will see copper streaks, when they get big wenough time to remove it. how big is to big thats up to you to decided.

I just threw out my bottle of shotters choice after 8 years the ammonina leftr the soloution. I dont plane to replace it as  butch's bore shine is an excellent copper remover as well and works great on carbon to boot.

Perfectly safe to use. Use a regular solvent like CLP, Shooters Choice, Hoppes, etc to get all the carbon fouling you can out, then use a jag and patch to swab the bore with the Copper Remover; a few passes is better than just one,  then let it sit for 10-15 minutes, get a clean patch soak it with the copper remover and "scrub" the bore with that. Patches will come out blue-green, the darker the color, the worse the fouling was. Repeat untill you are happy with the color the patches come out... I dont strive to get all the copper out, just the heavy deposits.

Now the most important part: dont leave the bore with this stuff in it, always patch with regular solvent a few times to make sure you got all of the copper remover out, then any oily patch (CLP is fine, I use FP-10) Dry patch before your shoot it again.  The copper remover will attack stainless or bare metal rods, and brass jags and loops, so always wipe down your rod and tools with an oily rag after using the stuff.

Using a brush isnt necessary with the copper removers like SC Copper remover  or Sweets 7.62, as long as you get the carbon out first, they work by chemical action.  Save the brushes for the carbon deposits.

Whenever using a copper solvent...or any solvent...I would flush the bore out with a couple patches of isopropyl alcohol to remove any solvent residue and dry patch before oiling.I would not use other solvents to flush ammonia based copper solvents from the bore.The results could be nasty.
Raymond