I recently de-coppered the barrel of my old .243 Rem M700 using Montana Extreme. Fired a 3 shot fouling group with Winchester Deer Season 95 gr loads that printed 5/8 of an inch. Then 95gr gr partitions in a handload over 41gr of H4350 that “grouped” at 3 to 4 inches. What the hell???
Was the handload something you previously worked up, or something you just threw together? Your OP is a little vague. Thread title talks about "decoppered 243", and then you state your rifle shot a 5/8" group. No info to go off of as far as I can tell.. You are either telling us you shot 1 3 shot group from the factory ammo, then moved on to the handloads. There's not statistical basis to go off of there. Shoot some 5 shot groups with the factory ammo. If you are still shooting 5/8", your rifle is good to go. You should be able to best any factory made ammo, with a tailor made handload. That is if your rifle likes the bullet you are using.
