Find this thread both interesting and strange. Chris says his groups open up, and i believe him, but mine never do and never have that i remember. Only rifle I really shoot now is MK1 Rapid17FT, it has never needed the barrel cleaning, by me anyway.
Ben Taylor cleaned it but after being re-leaded it was fine and remains fine. Solid 1/2" groups still after all these years with Crossman Premiers 7.9s. My XL1 is the same too.
So, is it the barrels of today, pellet material or lube that is on them? I tried JSB in both rifles, XL1 liked them best but they move more in the wind and vary more than the premiers.