I'm certainly no expert and agree that you should follow the recommendations of the manufacturer for cleaning and maintenance. I am under the impression that chrome lined barrels are fairly indestructible and have seen no damage to the ones on my SKS or AK.

Some rifles are more accurate when not totally clean. Benchrest shooters often use a "fouling shot" or shots to get the best results. Some do not clean their barrels at all. So the statement that some copper in the barrel may enhance performance may be accurate.

Again, I stand to be corrected as this is all hearsay and not from my personal experience.