I use both, but a friend of mine who shoots much more than I do has run into some carbon problems with the 4350. He is a high volume shooter, so, I sure that plays into it, shoots suppressed as I do, and that may be part too, but his 22 CM's and 6.5's have all demonstrated this propensity for carbon rings in the chamber with H4350. He finally bought him a bore camera, and pays much more attention now. He cleans his rifles after every range session, and I only clean mine when accuracy starts to fade, and I do use a carbon and copper remover when I do. I have never had any issues, but he probably shoots 100 rounds to my every one, maybe 1000.