Scope Mount & Ring Sizing Guide

One of the most important—and often most frustrating—parts of installing a scope is choosing the correct ring height and mount size. For maximum accuracy and reliability, your scope should sit as close to the bore axis as possible without interfering with rifle function.

To give you flexibility and confidence, Stiver Optics offers rings in four heights, along with precision-machined mounts that maintain a consistent, predictable profile.

Four Critical Scope Clearance Measurements:

1. Proper Ring Spacing: The distance between rings must align with your scope’s main tube and mounting area. Improper spacing can cause mounting stress and accuracy issues.
2. Objective Bell Clearance: The front of the scope (the objective bell) must clear the barrel without making contact. This is especially important with larger objective lenses (e.g., 50mm+).
3. Magnification Ring & Eyepiece Clearance: The magnification ring and eyepiece must clear both the rear mount base and your rifle’s bolt shroud or safety.
4. Bolt Handle Clearance: The bolt handle must cycle freely without contacting the scope—a common issue with classic bolt-action rifles and low-mounted optics.

1. Proper Ring Spacing

This is the most critical.  To check that the scope will work with the Stiver System.  With scope and rifle in hand, place the power ring, so the  muzzle end of the power ring, sits over the rear most mounting screw.  With the scope held in place make sure the objective bell start after the front most mounting hole.  Continue to B, if it does not, please contact us for help ensuring the mounts will work

1. Ring Height Options

Unlike original Buehler bases that varied in height, all Stiver Optics mounts are machined to a consistent  top height of 0.250" above the front ring. This gives you a reliable starting point for setup and reduces guesswork.

Our scope rings are available in four heights, measured from the top of the base to the bottom of the scope tube:

• Low – 0.100"
• Medium – 0.150"
• High – 0.200"
• Extra High – 0.250"

These 0.050" increments give you precise control over scope position without sacrificing strength or aesthetics.

How to Check for the correct size for your Rifle Scope Combinations

To check what size you need, it is important to mock up the scope at the proper height.  THe best way to do this is with playing cards,  having a caliper   on hand would help as playing cards come in different thickness and you will have two decks. Below is using standard Bicycle brand Playing cards. Each card is about 0.012 thick.  All examples below are erroring on the smaller side. 

First reference the information below, the rear stack should start with an amount of card extra to bring it to even with the front ring.  Start by creating two stacks of 29 cards. Place this on top of the front ring and add them to the rear stack.  Place the scope on top of the card stack on the gun.  Check that 4 cards will slide down the barrel so there is at least 0.05 clearance at point A.

If 29 cards does not produce the need gap, or is touching, increase the number of cards according to the chart below. 

For the Rear you will need to add the following number of cards, do to the fact the rear ring is lower then the front

• Remington 700-------------------5 Card
• Winchester 70--------------------6 Cards
• Whether by Mark V--------------7 Cards

Once you have the scope to the proper height,  Continue to C.

1. Power Objective Offset 

The power ring had to rotate for the scope to function properly. To ensure that it will rotate, you have to know the offset between the Main body tube and the power ring.  Stack cards on the main tube, push them over the power ring, pull off the cards that do not contact the tube.  Count the cards and calculate the offset.  Bicycle cards are 0.012 thick.    All Stiver mounts have at least 0.15 recess behind the rear ring.  Add that to the high of the ring choice during step B.

(Right Height +0.15) > (Offset)

1. Scope Handle Clearance

With the card stacked and the scope held on the center line.  Open the bolt handle, but with the action still closed, place 2 cards along the eyepiece, ensuring that the bolt will cycle with the cards in place. 

Hint: 

>It can be helpful to mount the rifle in a vice or mount,  also a second set of hands can be helpful

>Using a rubber band to hold the card together is also a helpful tip.

Need help choosing the right setup? Contact us or send your scope and rifle specs — we’ll help you find the perfect combination.