By Mark V. Lonsdale, STTU Training Director

While running the return to zero evaluations in the previous article, we decided to try moving the mount further up the rail to see if it made a difference. We were using an American Defense UIC rifle with an AD cantilevered mount and a Leupold scope, so already knew that we were using high quality products that consistently returned to zero when removed and replaced.  But when we moved the mount forward on the rail, the result was a dramatic shift in point of impact.

In the image above you can see the placement of the scope mount at the forward edge of the received. The cantilever overhangs the fore-end handguard, but the actual mount is on the receiver. This is the same index reference we used for all the previous tests.

When the mount was moved one slot forward on the Picatinny…