Disclaimer

Researched guidance, not professional advice

RifleScopeCalc publishes researched guidance compiled from published manufacturer specifications, published optical and ballistic formulas, and the consensus of verified owner reviews. We do not test products in person and we never claim to. Nothing here is a measured result, a professional recommendation, or a substitute for a qualified gunsmith.

Firearms safety comes first, every time

Treat every firearm as loaded until you have personally confirmed otherwise. Open the action and confirm the chamber is visibly empty before you mount, level, torque, lap, bore sight or measure anything, and leave the action open while you work. Point the muzzle in a safe direction throughout.

Confirm a zero only on a supervised range or a safe, legal backstop. Know your target and what lies beyond it. Follow the law where you shoot and hunt, including rules on land access, permitted cartridges, seasons and licensing, which vary and which are your responsibility to know.

An optical chronograph is placed downrange of the muzzle. Set one up with the action open and the rifle unloaded, and confirm your alignment before every string.

The limits of the calculators

The calculators are planning tools. Some of their outputs are exact and some are approximations, and the difference is stated on every page.

Exact: angular subtension in MOA and mils, exit pupil, twilight factor, relative brightness, ring height geometry, and the cosine component of an inclined shot.

Published formulas: the Miller Twist Rule for gyroscopic stability, and the lag time method for crosswind deflection. Both are widely used estimators, not measurements.

Modelled: all trajectory output uses a G1 point mass solver from the ballistic coefficient the manufacturer publishes, in a standard sea level atmosphere. It does not use radar derived drag data, and it does not model spin drift, Coriolis or aerodynamic jump. It is good to a few percent inside about 600 yards given an accurate muzzle velocity, and it becomes progressively less reliable beyond that, particularly as a bullet approaches the speed of sound. Confirm every figure on paper at a measured distance before acting on it.

The single largest source of error in any of this is muzzle velocity. Catalogue figures come from test barrels that are not your barrel, and a difference of 100 feet per second is ordinary.

Sourced figures and shooter convention

This site labels which is which, because a reader looking at a table cannot otherwise tell them apart. A sourced figure is exact arithmetic or a published standard. Shooter convention is something the hobby has settled on without a standards body behind it, including the treatment of one MOA as one inch at 100 yards, the eighth of an inch of objective clearance, and every ring height marketing name. Convention is useful. It is not a specification.

What we do not cover

This site covers optics and the hardware that mounts, levels, protects and supports them. It does not cover firearms, ammunition, reloading, gunsmithing, or anything requiring a licensed dealer, and nothing here should be read as guidance on any of those. Where a ballistic figure names a load, that is a disclosure about the arithmetic and not a recommendation.

Prices and availability

Prices and availability shown are as at the time the page was last compiled and change frequently. Every total on this site is a planning figure. Confirm current pricing before purchasing.

Accuracy and corrections

We work hard to get the numbers right and we will get some of them wrong. If you find an error, tell us and we will correct it. Specifications change without notice and manufacturers revise products mid-production, so verify any critical figure against the current manufacturer documentation for your exact model before relying on it.

To the fullest extent permitted by law, RifleScopeCalc accepts no liability for any loss or damage arising from reliance on the information published here. See also our terms of service and our affiliate disclosure.