Abstract: An optic mount modular system includes a bridge portion that is mounted on the top rail of a firearm. The bridge portion can have either an integral optics riser on which a sight can be mounted, or a top rail section. The bridge portion has a front end and a rear end, each of which have a vertical face in which there is a horizontal bore. At the top of the bridge portion at the front and rear ends there are horizontal interfaces or surfaces in which there are vertically oriented threaded bores. Accessories such as rail extension portions and magnifier mounts can be mounted to the bridge portion at the front and rear ends. These accessories can include an alignment pin or protrusion than extends from a vertical face that mates against the vertical face at the front end or rear end of the bridge portion, and the alignment pin or protrusion will fit into the horizontal bore of the front or rear end.
Abstract: Known “good” reference lines are provided for scope leveling using a reference device support platform attached to a rifle such that the reference device support platform first surface is parallel to rifle's horizontal bore center line and perpendicular to rifle's vertical bore center line. An alignment reference device, such as a laser leveling device, is then placed on the reference device support platform. When the alignment reference device is so placed, a horizontal axis of the alignment reference device will be parallel to the rifle's horizontal bore center line and a vertical axis of the alignment reference device will be perpendicular to the rifle's horizontal bore center line. Consequently, when vertical and/or horizontal reference lines are generated by the alignment reference device they are known “good” reference lines to be lined up with the scope's stadia lines.