I am seeing little to zero copper fouling as well in 20" 223 service rifle barrels.
I just give a fairly Quick Butches Bore shine with bronze brush and patches every 250 - 300 rounds and then every 600 I go more thorough following up the Isso Paste similar to explained on Frank and Theresa's Comapss Lake website at
https://www.compasslake.com/index.p...ducts_id=370&zenid=aasehugcs44ubgjmgnck59qrc0
I truly get the feeling AR Comp burns cooler and preserves barrel live wit hthe loads I am using in 20" service rifles. 23.0 grains +/- behind 62's, 68's 73's 75 VLD's and HPBT's and 80,5 and 82 grain 600 yard loads.
If I am correct about it actually burning cooler that may also be the reason for little to no copper fouling.
Dunno if fact and not really planning on overthinking it.
When something works I just roll with it till it don't...
Cheers,
George