How to select the correct Tier One scope mount

Mount Height

• Determining the right height
  • First rule of thumb: All Tier One scope mounts in Medium height are designed to work with a 56mm objective on a hunting rifle. If you have an AR platform rifle, or no barrel taper, or a full length picatinny rail and you have a 56mm objective then you might need the High version. Check using the following method.
  • Measure the scope objective's outer diameter (if the manufacturer states 56mm, it's probably a couple of mm larger for the whole housing - include the whole housing diameter in your calc).
  • Calculate the theoretical minimum height (this is calculated by halving the outer diameter e.g. Outer diameter is 60mm, theoretical minimum height is half of that, 30mm.)
  • Adjust for the actual, practical minimum height by considering personal preferences (how high you want it for eye relief), lens caps (these add a couple mm), and tilted mounts (20MOA/6MIL) and any other forend mounted accessories that might get in the way. 
  • Key Takeaway: Ensure adequate clearance for the scope to avoid contact with the rail or rifle, while also accounting for lens caps and sunshades. Keep in mind that, under heavy recoil scopes can and do flex, and if you only leave 1mm clearance above your barrel then the scope can hit the barrel during that flexing motion.

Cant (Tilt) Requirements - MOA/MIL

• Incorporating longitudinal cant in your setup for long-range shooting is important. Here are some guidelines:
  • We recommend stick to the minimum needed cant to maintain sight picture quality
  • The typical optimal cant across your rail and mount is going to be: 6 MIL (20 MOA)
  • If you are shooting very long range you may add additional cant with a canted picatinny rail (also called a scope base, action rail etc.)
  • Key Takeaway: Choose a mount with a tilt that provides enough adjustment range for long-range shooting without negatively impacting image quality.

Adjustment Range Optimization

• Selecting appropriate cant for optimal adjustment range
  • Choose a cant equal to half the scope's elevation range
  • Example: Nightforce ATACR 5-25x56 F1 scope (30 MIL/104 MOA max elevation) should have no more than 15MIL (52 MOA) tilt across the mount and rail. With a Tier One 6MIL rail, and a Tier One Monomount 6MIL, you can achieve 12MIL overall. 
  • Key Takeaway: To maximize the available adjustment range for long-range shooting, select a mount with a tilt equal to half your scope's elevation adjustment. It is not advisable to exceed half. 

Example:

• 6.5 Creedmoor rifle used up to 1000 meters
  • Recommended total cant (this is total, across your rail/scopebase and mount: 6 MIL/20 MOA)
  • Reason: This provides sufficient elevation for the intended use, and because you haven't added too much cant it reduces optical defects at closer ranges
  • Key Takeaway: Choose a cant suitable for your rifle's caliber and intended use to balance long-range shooting capabilities and image quality at closer ranges. 

Zeroing Limitations

• Over-tilting consequences
  • Using a rail and mount setup with more cant than half the scope's elevation adjustment makes zeroing at 100 meters impossible. This is because you'll not be able to wind the scope down low enough to overcompensate the total in-built cant in your mounting hardware.
  • Key Takeaway: Avoid using excessive cant to ensure the ability to zero your rifle at standard 100-meter distances.