The 5R design is supposed to help with copper fouling.....so they say. I can't think for the life of me what this guy's name is, I think he's from texas, puts on shooting schools and what not but he is a big believer in not cleaning copper out until it starts effecting your shooting, I guess up to a point, fouling improves your shooting. I for one have always been big on cleaning it out after each trip to the range but 2 years ago I went along with his mindset and was getting 40-50 rounds in, just using solvent for cleaning and didn't really notice any issues with accuracy. Once I shot around 50 rounds, then I'd clean out the copper. It would take a couple over nighters wit wipe out to get the job done though....