A friend just bought some concentrated ammonia from a place that handles commercial cleaning materials. I offered an old M-70 in .308 Win. with a very rough bore for a test. The rifle had been cleaned, very little carbon, but it looked like a gold mine inside. First couple of patches came out <font color="blue"> </font> blue <font color="black"> </font>, we are talking bright blue. In very short time the patches started to diminish, we even ran a bronze brush soaked in the ammonia down the barrel and got a dribble of blue liquid out the bore. Some of that was the brush being attacked no doubt. Anyhow, the result was an incredibly clean barrel, I scoped it and we found pits and gouges in the grooves that account for the fouling tendencies. Now I have to foul it up again, since it shoots terribly when it has been cleaned, then it settles back to 1.5" for the next 500 rounds or so. I usually clean this barrel every 500 rounds since it is on the rig we use to practice on my moving target system. Anyone else use industrial strength ammonia to clean their barrels - not sure I would use it on a custom barrel but it sure did the job on this old copper fouler.