When breaking in a barrel, a good practice to use is shoot the gun 5-10 times and clean it. shootin the gun 10-15 times and clean it again. shoot the gun 50 times and clean.....at this point I would take a wire brush and some copper solvent and get a soft brush to apply the solvent and let it sit for about 15 mins....then take the wire brush and run it up and down the rifleing of the barrel (letting the brush twist as it goes) this will smooth out all the rifleing in the barrel. do this until you dont see anymore "blue" come out of the barrel with the cleaning patches and shoot 100 rounds through it and clean it again.....at this point the rifleing should be smooth and the nick on the gas port should be gone as well. I have found that when doing this initialy you will get better accuracy out of your gun. The reason for doing this is because all "new" barrel have sharp edges on the rifleing of the barrel....when they cut the rifleing in it will allways leave these "sharp" edges......unless it is a match grade barrel and then this process is basicly done for you.