Thiking about re-building this rifle: The Lilja bbl has been good getting 0.30" groups (measure c-to-c) But I'm told the bbl mounting system (grub screws) is less than ideal. I want to stick with the CZ 457 action and MPA chassis - just re-barrel, add a tuner etc for max accuracy. Doable? Barrel / tuner recommends? Thanx.