Rifleman Q&A: Riflescope Shims

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posted on September 16, 2022
Qa

Q. I was attempting to sight-in a Winchester Model 94 side-eject rifle in .30-30 Win. using a telescopic sight. The shots printed high with the elevation cranked all the way down. Am I right to conclude that placing shims under the front telescopic sight base should correct this problem? How many shims of what thickness would be required?


A. Shimming the front base will depress the barrel relative to the line of sight. The old formula is the sight radius in inches, divided by the range in inches, times the error at the target. To get an idea of the thickness needed, this formula could be modified, substituting the distance between the rings for the sight radius. Maximize the scope’s range of adjustment by determining the error at the target with your elevation adjustment set near the middle of its limits.

­—John Treakle


This “Questions & Answers” was featured in the February 2006 issue of American Rifleman. At time of publication, "Questions & Answers" was compiled by Staff, Ballistics Editor William C. Davis, Jr., and Contributing Editors: David Andrews, Hugh C. Birnbaum, Bruce N. Canfield, O. Reid Coffield, Charles Q. Cutshaw, Charles M. Fagg, Angus Laidlaw, Evan P. Marshall, Charles E. Petty, Robert B. Pomeranz, O.D., Jon R. Sundra, Jim Supica, A.W.F. Taylerson, John M. Taylor and John W. Treakle.

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