Couple of other possibilities:
Is the barrel free of plastic residue from all that shooting?
Is your bench setup and shooting technique solid? Light MLs shooting moderate to heavy charges are pretty lively and light rifles are especially tricky, even relatively light-kicking CFs. Sometimes how they sit on the bags makes a big difference and can take some figgering out. When you can, latch onto some BH209.
You’ll get it. Good luck.
