Newfound Wolf:
I am going a little long...
I am not an expert on Copper Pellets but I would recommend you that you NEVER shoot anything but quality LEAD pellets...There are a lot of marketing gizmos out there, resist the temptation to engage in using any of them in your fine guns...LEAD QUALITY PELLETS is the name of the game for precision and to preserve a good barrel.
The last time I saw those copper pellets they were actually copper plated lead pellets, if this still applies, then you must be getting copper color on your patches and there is nothing to worry about...You will not have layered copper around your barrel's bore...So the same rules for cleaning a barrel discussed in this thread apply...
Now, if you are uncomfortable and want no traces of copper color in your barrel and your barrel is NOT STAINLESS STEEL, use any good AMMONIA based copper solvent used for centerfire guns and follow the instructions from the manufacturer....If your barrel is made out of stainless, I would use any good penetrating oil (let it penetrate overnight) followed by moderate scrubbing. Ammonia can attack stainless if you don't know how to use it, and if you don't, stay away from it...Nevertheless, Ammonia is harmless to Chrome Molly and to the soft steel used in Walther Lothar air gun barrels. Some people believe WL air gun barrels are made of Chrome Molly but they are not, nevertheless you can place an order of at least 10 and have them make them in pretty much any steel material & twist that you desire.
I am going to get off the topic and pass you a good experience...Back in the 60's DAISY came out with steel darts and MARKSMAN manufactured a low power pistol for shooting them...At the time I had a Diana Mod 27 (outstanding rifle) and I shot those darts hundreds if not thousands of times with that break barrel rifle...Later in my life I rebuilt all of my youth's guns and I bore scoped, air gauged and slugged that Diana's barrel and found out that the barrel's dimensions were still within tolerances, but the rifling was dull and not sharp...No big issue for a plinking gun, but the precision it once had was not going to return ever...You never shoot a projectile harder or close to the hardness of your barrel and this was a good example...But hey!, shooting is about having fun and I had lots of it.
About 5 years ago I bought some cheap Crossman barrels for doing some lab testing and machined one of those for my Anschutz 9003 and some others for a few friends of mine...We shoot steel BB's, steel darts, custom tungsten pellets, etc. with consistent power coming from guns that I know are some of the most precise currently in production. We shoot steel darts at a dart roulette set at 50 meters and play the games that you play with hand thrown darts...We use 50 meters because at that distance the darts don't go though the roulette board and we can detach them easily with our hands and at that distance you can still shoot with good accuracy....So if you want to shoot steel BB's, steel darts, tungsten pellets or whatever, buy one of those cheap barrels (no choke) and fit it to your gun and by all means DO NOT restrain yourself from creativity and fun.
Regards,
AZ