AR. Heavy barrel non chrome lined.
Give a good cleaning before you fire for the first time. No telling what kinda trash is in the barrel from manufacturing, test-firing, storage and shipping.
1. Fire 1 round and clean for the first 5 rounds.
2. Fire 5 and clean for the next 20-25rds.
3. Fire 20rds and inspect. If it is fouling up, clean it, then clean it every 20 for the next 100rds. If it isn't fouling up, you're done with any special break-in steps.
I recommend Montana X-treme Copper Killer as a bore cleaner. Quickest copper remover I've ever used, but safe on steel (unlike Sweet's 7.62 and similar cleaners.