What cartridge are you shooting that gets 20k rounds through the same barrel?
#8 and #10 are both my rifles. #8 has more than 20,000 rounds on it without ever being cleaned; and #10 is a 6XC with +/- 700 rounds on it without ever being cleaned.
8). Tikka T3 Lite 223, suppressed, with SWFA fixed 6x scope. UM ammo.