How to Calculate What Scope Ring Height I Need

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What size of scope rings do I need? This is a very common question. Without having all of your components in hand it is very difficult to give an accurate scope ring height. For this reason, we have provided a scope ring height formula to help you determine the proper ring height required. The formula will vary slightly depending on the type of chassis you are measuring for.

(All units in inches. Ring height measured from top of base to scope center line. Sloped bases add .035" to height every six inches objective extends from base.)

For standard Evolution chassis: (actual objective diameter/2) + .9 - (action diameter/2) - base height = required ring height.

For Evolution HD / Carbon chassis: (actual objective diameter/2) + 1.05 - (action diameter/2) - base height = required ring height.

We will now work through an example using the formula for a standard Evolution Chassis:

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Using the above formula, we will plug in some numbers. Our scope in this example has an objective lens diameter of 50 mm. We must convert this to inches, which comes to 1.96. The Remington 700 SA has an action diameter of 1.35 inches. Finally, our scope base is un-sloped and has a height of .350 inch from the bottom of the base to the plane in-between the risers on the Picatinny rail.

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The equation is solved in the above photo. In our example we need .855 inch of ring height. Our scope has a 30mm tube, so we choose the XLR 30mm Medium Profile Scope Rings which have a height of 1.18 inches. The extra space should be enough for our lens covers.

The use of a caliper is recommended for taking measurements. It is also important to note that all units are in inches-be certain to convert before placing your dimensions into the formula. The formulas provided do not guarantee correct fit. Use your own discretion.

Questions? Concerns? Comments? Email us at info@xlrindustries.com