My 300 wsm Montana is shooting right at 1/2" now for three shots @100 yds. I drilled out the front guard screw hole(pillar) the next drill diameter larger on mine. Guard screws should not make contact with the stock except at the head. Also check your bolt lug contact, I had to lap in my lugs on this one and a 338 Federal, only one lug on each rifle was contacting the reciever. My guard screws are super tight also.
These are really nice rifles when their shooting well.
