On, Off, On, Off
How Good Are Quick Detachable Mounts?
How many times have you heard the statement, “These mounts return to zero… perfectly”? You’re left with the impression when the detachable mount is taken off and returned, it has no effect on zero or the grouping ability of the rifle and load. Is that true, advertising spiel, or just an aberration?
To test the statement’s validity, I chose three of what I consider the best quick detachable mounts on the market and three excellent shooters. I used a very accurate rifle, capable of .3″, 5-round groups. The groups were shot using a Harris bipod in the front and a competition benchrest bag in the rear.
The handloaded rounds were tuned prior to the test to deliver groups in the .3″ range. The same brass was loaded carefully each time, with five loadings each for the duration of the test. The test rifle was a custom built .308 from Nighthawk with a proven tactical scope.
The tests were conducted at 60′ elevation (approximately sea level), approximately 75 degrees F, 70 percent humidity, and a barometric pressure of 29.90″ of mercury.
The range was 100 yards. To set a benchmark, two of the shooters shot three 4-round groups using normal, tactical rings not removed. The aggregate for shooter one was .338″ and for the second .361″. The overall aggregate was .349″ for six groups of four rounds each. All groups formed in approximately the same location at or slightly below the center dot. It was hoped the zero would not obliterate their aiming point (the center dot) as shots were fired. All but one shot was either in or touching the 1″ inner ring. All were at approximately the same location inside the 1″ ring.
Story By: Jacob Gottfredson
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