Mine came 2nd hand with the rifle (Tikka T3X in .223) and after a season of shooting with them, my friend put it through his sonic cleaner and was amazed that virtually nothing came out of it, this was over 4 years ago and it's never been cleaned since! Got no plans to repeat this process as I think it would be a pointless exercise so my suggestion would be not to bother other than add a bit of copper slip on the muzzle thread.