I have a Colt hard chromed AR-15 barrel that is over 15 years old and has had several thousand of rounds through it and it still shoots sub 3/4 MOA which is how it shot when it was brand new

My 22 Cheatah went from sub 1/2 MOA to over 1 MOA after about 800 rounds but it will still take out a coyote with one shot at 200 yards.....but not a prairie dog at 300 anymore unless I get lucky on the first shot. (It is now a tomato stake.)