I run TBAC cans with their brakes that are "permanently" mounted with red Loctite to the barrel (not intended to be removed for the life of the barrel, but can be removed with heat so the brake/mount can be installed on the new barrel when it's time to replace the old one). You cannot clean the crown of the barrel with the brake on because you cannot access it. I asked TBAC what they recommend about cleaning the crown and they said, "We don't clean them, and it doesn't affect anything regarding accuracy". I reluctantly followed their lead and currently have a 6.5CM barrel with over 3200 rounds, a 300NM barrel with nearly 1500 rounds (both near the end of their service life) and several other barrels in other chamberings that are mid-life. Due to the "permanently" mounted brakes, none have had the crown cleaned since new, and none have experienced any degradation in accuracy. I know the 6.5 and 300NM are going to start going south soon, but that will be due to round count/throat erosion.