Thanks for the replies...
It is a chore to clean the barrel as often as every 50 pellets. I've tried VFG felts for cleaning and also I have a Napier pull through kit.
The Napier kit seems to give better results, tighter post clean groups but I wonder about inserting a metal loop into the barrel....
Any thoughts on these or other cleaning techniques?
I estimate that since the rifle was new it's had 3 to 4 thousand pellets down it but the groups still open up after about 50 shots..