Gun sight zero checking device

A method comprising:

• providing a rifle having a rifle scope mounted thereon, said rifle having a chamber, said rifle scope having been sighted-in for said rifle,
• providing a sight-in checker device comprising
• a mandrel for closely fitting the rifle chamber, said mandrel having a longitudinal axis, a front end, and a back end;
• an arm mounted to the back end of the mandrel and extending transversely outwardly from the longitudinal axis of the mandrel;
• a bracket mounted to the arm for mounting a checker scope to sight along a path approximately parallel to the axis of the mandrel, and
• a checker scope mounted to said bracket, said checker scope having been sighted-in to coincide with the sight-in previously determined for the rifle scope when the sight-in checker device is placed in a predetermined position with respect to said rifle,
• wherein the checker device further comprises a stop to contact an outer surface of the rifle scope when the checker device is in the predetermined position,
• positioning the mandrel of the checker device in the chamber of the rifle;
• positioning the checker device in the predetermined position with respect to the rifle;
• positioning the rifle in a stable position with the rifle scope centered on a target;
• and
• viewing the checker scope to determine whether it is also centered on the target.