CR-10 has never caused me any problems. I usually leave it in the bore from 10 to 15 minutes at a time. Lately, though, Wipeout is what I've been using mostly for copper fouling just because it's easier to use. I've also tried Coppermelt and didn't have very good experience with it. My first bottle arrived totally empty, the pressure that had built up inside the bottle caused the cap to unseal and it all leaked out in transit. The replacement bottle also had some leakage, but90% or better was still in there.After using it, however,I wasn't impressed and since it cost about $30a bottle, I won't try any more. I'll give this KG12 a try and see how I like it. I also want to try Montana Extreme 50BMG. The guys at Sinclair Int'l really like it. One of these days I might actually find the ultimate bore cleaner, but I doubt it.