o ring or the shims in our optima, accura and wolf make them pretty much the simplest muzzy to clean. Remove BP, hot soapy water with a brush after using the drill bit, dry it and I am finished with that part. A few patches of 2 in 1 bore scrubber and bam, its finished. I do however take my time as I prefer to treat them right and make sure its done right. If I worried about how long it took to clean a muzzy, I wouldnt be shooting one.