These tubes are used to align the scope rings on the bases during tightening of the base screws. As scope tubes are very thin aluminium and are easily bent and distorted, it is best not to use the scope for the alignment of the rings on the base mount.
The scope rings are located on the rifle and the retaining screws are taken up finger tight only so that they can be slid along the mount to obtain the required eye relief for the scope.
After the location of the scope rings has been determined to give the required eye relief for the scope, the scope is removed from the rings and the correct tube is located in the rings and the scope retaining screws tightened to the recommended torque. This locks the alignment tube up tightly in the scope rings.
The scope ring base screws are then tightened to approximately half the recommended torque for that screw size and the alignment bar is then tapped lightly with a soft hammer to bed the scope ring bases into the dovetail or Pic/ Nato rail. The screws are then tightened to their required torque and the alignment bar is then removed from the rings and the scope refitted and tightened to the required torque for those screws.
The tubes are supplied in the four common sizes,1″ (25.4mm), 30mm, 34mm and 35mm and are a thick walled 316 stainless tube machined to precision tolerances very slightly smaller (maximum of 0.001″- 0.025mm) than the scope tube diameter.