Never, and I don't break them in either. After accuracy drops off (My 308 is around 600 with Varget or 8208 on a Bartlein....not sure on my new 260 as I have 500 on a Kreiger and it still bugholes), I use a squirt of Gunslick Foaming Bore Cleaner, 20 minutes of rest, and 5-7 patches. If i'm in a hurry, then a bore snake will suffice.
My 223ai went 800 on the barrel (Rock) before I cleaned because I couldn't stand it.

