Which part of the copper coat on a HMR bullet (which does it's best to weld itself to the inside of your barrel) will make it better by leading the barrel?
Term of speech my friend, keep your hair on
In my experience my HMR doesn't like cleaning, many people find the same.
I will GUARANTEE you any HMR with a good true barrel will shoot better clean than dirty.
Was your barrel filthy and lined with copper residue when you got the gun new?
Barrel cleaning has been discussed many times on this and other forums. Cleaning any rifle, particularly the little HMR