Ring height by objective
Objective Diameter and Ring Height Chart
Quick answer
A 40mm objective needs roughly 0.99 to 1.07 inches of ring height to clear the barrel, and a 50mm objective needs roughly 1.19 to 1.27 inches, regardless of tube diameter. The required height comes from the objective bell, not the tube; tube diameter only decides which stocked ring product is available to buy.
The height a ring needs to clear an objective is set entirely by the objective bell, the housing around the front lens, and never by the tube diameter in the middle of the scope. A 40mm objective on a 1 inch tube and the identical 40mm objective on a 34mm tube need the same clearance at the front of the scope, because the bell is the same size either way. What changes between tube diameters is only which specific stocked ring product is tall enough and sized to fit.
This page runs that arithmetic for every objective size sold in this catalog, against every tube diameter, using the objective lens diameter, a realistic 4 to 8mm housing wall, and the eighth inch clearance convention used throughout this site.
These figures are computed from published objective lens diameters and the standard clearance convention, not measured from disassembling a specific scope.
Ring height needed against objective diameter, by tube size
The working
Bell outside diameter = objective lens diameter + 4 to 8mm of housing wall. Ring height to centre = (bell OD / 2) + 0.125 in clearance.
The height needed is identical across tube diameters, since it depends only on the objective bell. The columns differ because each tube's stocked ring line offers a different set of actual heights to choose from.
Read across for your objective size. The middle column is the exact height range needed, from the thinnest realistic bell to the thickest. The four right columns show the lowest stocked height in this catalog, for each tube diameter, that clears the objective with the full eighth inch of margin even in the worst case.
A 44mm objective needs 1.07 to 1.15 inches of ring height, and the lowest catalog ring that clears it with full margin is 1.50 inches on a 1 inch tube or 1.26 inches on a 30mm or 34mm tube.
Sourced figure
| Objective | Height needed (centre) | 1 inch tube | 30mm tube | 34mm tube | 35mm tube |
|---|---|---|---|---|---|
| 20 mm | 0.60 to 0.68 in | 0.76 in | 0.80 in | 0.92 in | no stocked rings |
| 24 mm | 0.68 to 0.76 in | 0.76 in | 0.80 in | 0.92 in | no stocked rings |
| 28 mm | 0.76 to 0.83 in | 0.95 in | 0.87 in | 0.92 in | no stocked rings |
| 32 mm | 0.83 to 0.91 in | 0.95 in | 1.00 in | 0.92 in | no stocked rings |
| 33 mm | 0.85 to 0.93 in | 0.95 in | 1.00 in | 0.95 in | no stocked rings |
| 36 mm | 0.91 to 0.99 in | 1.10 in | 1.00 in | 1.10 in | no stocked rings |
| 40 mm | 0.99 to 1.07 in | 1.10 in | 1.10 in | 1.10 in | no stocked rings |
| 42 mm | 1.03 to 1.11 in | 1.50 in | 1.26 in | 1.26 in | no stocked rings |
| 44 mm | 1.07 to 1.15 in | 1.50 in | 1.26 in | 1.26 in | no stocked rings |
| 50 mm | 1.19 to 1.27 in | 1.50 in | 1.50 in | 1.45 in | no stocked rings |
| 52 mm | 1.23 to 1.31 in | 1.50 in | 1.50 in | 1.45 in | no stocked rings |
| 56 mm | 1.31 to 1.39 in | 1.50 in | 1.50 in | 1.45 in | no stocked rings |
"No stocked rings" for 35mm is not an oversight: this catalog carries no 35mm ring product, and 35mm tubes are a small enough niche that rings for them are usually sourced directly from the scope manufacturer rather than a third party ring line.
Where does the housing wall estimate come from?
The bell outside diameter, the number that actually contacts the barrel, is almost never published by scope manufacturers. Only the lens diameter, printed as the second number in a scope's magnification and objective spec, is public. The housing wall around that lens is estimated conservatively rather than measured.
A 40mm objective lens sits inside a bell estimated at 1.73 to 1.89 inches outside diameter, a 4 to 8mm housing wall added to the published lens size.
Shooter convention
| Objective lens | Bell OD, thin housing (4mm) | Bell OD, thick housing (8mm) |
|---|---|---|
| 20 mm | 0.945 in | 1.102 in |
| 24 mm | 1.102 in | 1.260 in |
| 28 mm | 1.260 in | 1.417 in |
| 32 mm | 1.417 in | 1.575 in |
| 33 mm | 1.457 in | 1.614 in |
| 36 mm | 1.575 in | 1.732 in |
| 40 mm | 1.732 in | 1.890 in |
| 42 mm | 1.811 in | 1.969 in |
| 44 mm | 1.890 in | 2.047 in |
| 50 mm | 2.126 in | 2.283 in |
| 52 mm | 2.205 in | 2.362 in |
| 56 mm | 2.362 in | 2.520 in |
4 to 8mm across the diameter is a realistic range for a modern scope's aluminium housing wall, not a published manufacturer figure. Measuring your own scope's bell with a caliper always beats this estimate.
What "marginal" and "no stocked rings" mean in practice
A ring described elsewhere on this site as marginal for a given objective clears a thin bell and fouls a thick one, which means the actual outcome depends on a dimension nobody publishes. Treat a marginal fit as a measure-first situation, not a buy-and-hope one. Where this table shows no stocked rings, as with every 35mm entry, that reflects an actual gap in this catalog rather than a claim that no such ring exists anywhere; 35mm tubes are typically supported directly by the scope's own manufacturer rather than by third party ring lines.
An objective that falls between two listed sizes, such as a 46mm lens, sits between the 44mm and 50mm rows. Use the taller of the two neighbouring heights rather than interpolating, since the clearance margin exists precisely to absorb small differences like this one.
Sources
- Objective lens diameters as published by scope manufacturers
- Stocked ring heights, as listed in our catalog, by tube diameter
Frequently asked questions
What ring height does a 40mm objective need?
Roughly 0.99 to 1.07 inches from the rail to the centre of the tube, on any tube diameter. This is one of the most common objective sizes on hunting scopes and typically fits a low to low-medium stocked ring across 1 inch, 30mm and 34mm tube lines.
Does the required ring height change with tube diameter?
No. The height needed to clear an objective bell depends only on the bell's outside diameter, which is set by the objective lens, not by the tube in the middle of the scope. Tube diameter changes which specific stocked ring product fits, since rings are manufactured to one tube size each, but not the underlying clearance requirement.
What if my objective size falls between two rows on this chart?
Use the taller of the two neighbouring rows rather than interpolating. A 46mm objective, for example, sits between the 44mm and 50mm entries; choosing the 44mm row's ring height risks a marginal fit, while the 50mm row's height guarantees clearance with margin to spare.
Are there stocked rings for a 35mm scope tube?
Not in this catalog, and 35mm is a genuinely small niche in the wider market as well. Scopes built on a 35mm tube typically ship with rings from the scope manufacturer directly, or require a mount sourced specifically for that diameter rather than a general purpose ring line.
What does a "marginal" fit mean on this chart?
It means the ring clears a thin objective bell and fouls a thick one, and the actual outcome depends on a dimension, the bell's exact outside diameter, that manufacturers rarely publish. Treat any marginal result as a signal to measure your specific scope's bell with a caliper before ordering.
Why does a 44mm objective need a taller ring on a 1 inch tube than a 30mm tube?
It does not need a physically taller clearance; the required height is identical. What differs is which heights are actually stocked in each tube's ring line. A 1 inch line may skip directly from 0.95 to 1.50 inches, forcing a taller purchase than a 30mm line that offers a 1.26 inch option in between.
Researched, not professional advice. This page is compiled from published manufacturer specifications, published optical and ballistic formulas, and owner-review consensus, not hands-on testing. Figures described as a rule of thumb are shooter convention rather than sourced numbers, and they are labelled that way wherever they appear. Ballistic figures come from a point mass model using the ballistic coefficient the maker publishes, so treat them as a starting point and confirm them on paper at a measured distance. Confirm your firearm is unloaded with the action open before you mount, level, torque or bore sight anything. Verify a zero only on a supervised range or a safe, legal backstop, know what lies beyond your target, and follow the law where you hunt and shoot, including rules on land access and permitted cartridges.