I'm new to bolt guns and just got a LTR with a relatively heavy (4+ lb.) trigger and would like to adjust, but don't know which trigger the rifle has. The trigger face is smooth and has a hex screw in the upper part. Is this screw the adjustment? and if so, how do it work? I read that some LTRs came with X mark triggers and some with 40X, I don't know the difference. Thanks...