Re: OAL for 300 Win Mag in Ruger M77?
You need to be very careful with the measurement. I put a wooden dowel in the barrel until it touches the bullet tip (trapping the bullet between the dowel and aluminum push rod), using the dowel and the tool's aluminum push rod you can gently position the bullet repeatedly on and off the lands until by feeling you are sure you have the exact position. I'll do this and measure until I get the same measurement a few times.
Also when you tighten the push rod thumbscrew you need to be sure the rod doesn't move, the bottom of the screw applies a rotational force against the rod and it can move without you knowing it, you have to keep a slight touch on the rod when you tighten the screw, and don't tighten it much or it will move.
You've probably already had the bullet stick in the lands, the dowel ensures the bullet comes out with the tool after the LnL is tightened and removed. Also don't re-use the same bullet over and over too many times as it will engrave with the lands giving a false measurement.
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