Good point LP.

Some guns do have ribs that prevent an accurate measurement by laying upside down on a table because one end or the other is below the height of the barrels or because they have a middle bead. For those, it's best to use a long straight edge like a 36 or 48 inch rule.

Also, check your table you will use for flatness. Most have some warpage.

Last edited by Chuck H; 06/30/12 11:14 AM.