Finding the correct shotgun sight can depend on knowing the width of your shotgun's ventilated rib. Dealing in shotgun sights, we quickly discovered that rib dimensions are not standardized across manufacturers, models, or even different gauges and configurations of the same model. After years of trying to answer questions from customers regarding shotgun sight fit, we decided to compile the available information and build a database of shotgun rib widths (to the best of our ability).
Looking for thread specifications for your shotgun's front bead? Check out our shotgun bead thread reference.
This shotgun rib width chart brings together rib-width measurements and specifications from manufacturer manuals, published firearm specifications, professional firearm reviews, gunsmithing information, and owner measurements to make finding your shotgun's rib width easier.
How to Use This Chart
Find your shotgun manufacturer and model in the table, then check the gauge and rib width listed for that specific configuration. When a model is available in multiple gauges, we list the gauges separately when there is evidence that the rib dimensions differ.
Manufacturer identifies the shotgun manufacturer.
Model identifies the specific shotgun model or model variant. Where different configurations of the same model have different ribs, they are listed separately rather than being combined into a single entry.
Gauge identifies the gauge or chambering associated with the listed measurement. This is important because rib widths can differ between 12-, 20-, 28- and .410-gauge versions of the same shotgun.
Rib Width gives the measured or published width of the shotgun's rib. Measurements are provided in the units used by the original source, with an approximate metric or imperial conversion where useful. A measurement such as 10 × 8 mm indicates a rib with two relevant dimensions and should not be interpreted simply as a 10-mm-wide flat rib. Likewise, a range such as 10–8 mm indicates that the rib tapers from approximately 10 mm at one point to 8 mm at another.
Rib Profile describes the type or shape of the rib when that information is available. Terms such as ventilated, stepped, tapered, windowed, low ventilated, and sporting rib are included to help distinguish configurations that may have similar widths but different profiles.
Evidence Type explains where the measurement came from. Manufacturer specification or manufacturer manual indicates that the dimension was published by the shotgun manufacturer. Published measurement indicates that a firearm publication or professional reviewer measured or reported the dimension. Owner measurement identifies a measurement reported by an individual firearm owner. Other entries may be identified as historical manufacturer information or independent measurements.
Confidence indicates how strongly the available evidence supports the listed measurement. Very High generally indicates a direct manufacturer specification or manual. High indicates a published measurement or multiple supporting sources. Medium-High or Medium indicates that the measurement is based primarily on an owner report or other less authoritative source.
Important Rib Width Disclaimer
Shotgun rib widths can vary by model, gauge, barrel configuration, rib style, production year, and specific firearm. A model listed with one rib width should not automatically be assumed to have that same dimension across every version ever produced.
The measurements in this chart are compiled from available published specifications, measurements, and other sources. They should be used as a reference rather than a guarantee that a particular shotgun has the listed rib dimension. When selecting a shotgun sight, rib-mounted accessory, or other component that depends on rib width, always verify the rib width on your specific shotgun before purchasing.
Measured Width vs. Sight Compatibility
Some shotgun sight manufacturers publish compatibility charts that place a shotgun into a particular rib-width range. Those compatibility ranges are useful for identifying sights that are designed to fit a particular model, but they are not necessarily measurements of the shotgun's actual rib. For that reason, this chart prioritizes actual measurements and explicit manufacturer specifications whenever they are available.
Where an exact measurement could not be verified, we do not substitute a generic manufacturer's fit range and present it as an exact dimension. The database will be expanded as additional reliable measurements and specifications become available.
Why Rib Width Matters
Shotgun sights designed to attach to a ventilated rib are made for specific rib widths and profiles. A sight intended for a narrow rib may not properly fit a wider rib, while a sight designed for a wider rib may not securely attach to a narrow rib. Rib width is therefore one of the most important specifications to check before purchasing a rib-mounted shotgun sight.
If your shotgun is not listed, the safest approach is to measure the rib on your individual firearm and compare that measurement with the sight manufacturer's specifications.
Shotgun Rib Width Chart
| Manufacturer | Model | Gauge | Rib Width | Rib Profile | Evidence Type | Confidence |
|---|---|---|---|---|---|---|
| Benelli | M2 | 12 | 8 mm | Ventilated | Published/owner measurement | High |
| Benelli | Montefeltro | 12 | 8 mm | Low ventilated | Manufacturer manual | Very High |
| Benelli | Montefeltro | 20 | 8 mm | Low ventilated | Manufacturer manual | Very High |
| Benelli | Nova | 12 | 8 mm | Ventilated ramp | Published specification | High |
| Benelli | SBE 3 | 12 | 8 mm | Low ventilated | Manufacturer documentation | Very High |
| Benelli | SBE 3 | 20 | ~6 mm | Ventilated | Owner measurement | Medium-High |
| Benelli | SBE 3 | 28 | 7 mm | Carbon-fiber ventilated | Published review | High |
| Beretta | A300 Ultima Field | 12 | 7 mm | Stepped | Published review | High |
| Beretta | A300 Ultima Sporting | 12 | 7 mm | Stepped | Published review | High |
| Beretta | A300 Ultima Sporting | 20 | 7 mm | Stepped | Published review | High |
| Beretta | A400 Xplor Action | 28 | .200" / 5.08 mm | Ventilated | Published specification | Very High |
| Beretta | A400 Xtreme Plus | 20 | 7 × 7 mm | Ventilated | Published specification | High |
| Beretta | 1301 Competition | 12 | 10 mm | Stepped | Published measurement | High |
| Beretta | 686 Silver Pigeon I | 28 | 5 mm | Ventilated | Published specification | High |
| Beretta | 687 Silver Pigeon III | 12 | 6 × 6 mm | Windowed | Published specification | Very High |
| Beretta | 687 Silver Pigeon III | 20 | 6 × 6 mm | Windowed | Published specification | Very High |
| Beretta | 687 Silver Pigeon III | 28 | 6 × 6 mm | Windowed | Published specification | Very High |
| Beretta | 687 Silver Pigeon III | .410 | 6 × 6 mm | Windowed | Published specification | Very High |
| Beretta | DT11 Supersport | 12 | 10 × 8 mm | Channel | Manufacturer/distributor catalog | Very High |
| Browning | A5 Stalker | 12 | .250" / 6.35 mm | Ventilated | Published specification | Very High |
| Browning | BPS Special Steel Field | 20 | .250" / 6.35 mm | Ventilated | Published specification | High |
| Browning | Citori 725 Field | 20 | .250" / 6.35 mm | Ventilated | Published specification | High |
| Browning | Citori 725 Sporting | 12 | 5/16–7/16" | Canted sporting rib | Published specification | High |
| Browning | Citori 525 Sporting | 12 | 8–11 mm | Canted ventilated | Published specification | High |
| Browning | Citori 525 Sporting | 20 | 10 mm | Canted ventilated | Published specification | High |
| Browning | Maxus 2 | 12 | 6.5 mm | Ventilated/tapered | Published measurement | High |
| Caesar Guerini | Invictus Sporting M-Spec | 12 | 10–6 mm | Tapered | Published review | High |
| CZ-USA | Redhead Premier | 16 | 8 mm | Flat ventilated | Published specification | High |
| CZ-USA | Redhead Premier Target | 20 | 10 mm | Raised stepped | Published specification | High |
| Fabarm | ELOS N2 Sporting | 12 | 10–8 mm | Tapered | Published measurement | High |
| Fabarm | Wetlands | 12 | 10–6 mm | Tapered ventilated | Published measurement | High |
| Fabarm | Classis | 12 | 10–7 mm | Tapered | Manufacturer catalog | Very High |
| Franchi | Affinity | 12 | 8 mm | Ventilated | Published measurement | High |
| Franchi | Affinity 3 | 12 | 8 mm | Ventilated | Published measurement | High |
| Ithaca | Model 37 Ultra Featherlight | 20 | .250" / 6.35 mm | Ventilated | Published specification | High |
| Mossberg | 500 / 590 / 835 | 12 | .380" / 9.65 mm | Vent rib | Independent measurement | Medium |
| Mossberg | 940 JM Pro | 12 | 9.53 mm / 3/8" | Ventilated | Expert measurement | High |
| Mossberg | Gold Reserve Black Label Sporting | 12 | 10 mm | Ventilated | Published review | High |
| Remington | 870 Express | 12 | 7 mm | Ventilated | Published measurement | High |
| Remington | 870 Fieldmaster | 12 | .295" / 7.49 mm | Vent rib | Published measurement | High |
| Remington | 870 Compact | 20 | 5/16" / 7.94 mm | Vent rib | Owner measurement | Medium-High |
| Remington | 1100 | 20 | 5/16" / 7.94 mm | Vent rib | Owner measurement | Medium |
| Retay | Masai Mara | 12 | 8 mm | Ventilated | Published specification | Very High |
| Ruger | Red Label | 12 | .305–.325" / 7.75–8.26 mm | Vent rib | Published measurement | High |
| Syren | Julia | 20/28 | 6 mm / .24" | Parallel ventilated | Manufacturer specification | Very High |
| TriStar | Viper G2 Bronze | .410 | 5 mm | Ventilated | Published measurement | High |
| Winchester | SX3 | 12/20 | 6 mm | Ventilated | Model-specific evidence | Medium-High |
| Winchester | SX4 | 12 | .250" / 6.35 mm | Ventilated | Published specification | Very High |
| Winchester | SXP | 12 | .250" / 6.35 mm | Ventilated | Published measurement | High |
| Winchester | SXP | 20 | .250" / 6.35 mm | Ventilated | Published measurement | High |
| Winchester | Model 101 Trap | 12 | 10 or 15 mm | Trap rib | Historical manufacturer material | Very High |
Shotgun Rib Width FAQ
How do I measure the width of a shotgun rib?
Use a caliper to measure the rib at its widest point where the shotgun sight will actually attach. Measure straight across the rib rather than measuring the distance between the ventilation slots. For a tapered rib, measure at the intended mounting location because the width can change along the barrel.
Where do I measure a shotgun rib for an aftermarket sight?
Measure where the aftermarket sight will be mounted, not necessarily at the muzzle or the end of the rib. If the sight can be positioned at different locations, check the rib width at the location you intend to use. This is particularly important on tapered or stepped ribs.
Is shotgun rib width measured across the entire rib?
Generally, yes. Rib width refers to the outside-to-outside width of the rib at the point where the sight attaches. Do not measure the distance between the ventilation slots or the narrower surface at the top of a stepped rib unless the sight manufacturer specifically instructs you to do so.
What is the difference between a 1/4-inch, 5/16-inch and 3/8-inch shotgun rib?
These measurements describe the approximate width of the rib: 1/4 inch = 6.35 mm, 5/16 inch = 7.94 mm, and 3/8 inch = 9.53 mm. The difference may be small visually but can determine whether a rib-mounted sight fits correctly.
How do I know what size rib-mounted shotgun sight I need?
Identify your shotgun's exact manufacturer, model, gauge and barrel configuration, then compare its rib width with the sight manufacturer's specified fit range. If the shotgun is listed in our shotgun rib width chart, use the listed measurement as a starting point, but verify the rib on your individual firearm whenever possible.
Does shotgun rib width vary by manufacturer and model?
Yes. Rib widths are not standardized across all shotguns. Different manufacturers and models can use different rib widths, and even different configurations of the same model can have different dimensions. A manufacturer-wide assumption such as "all Benelli ribs are 8 mm" should therefore be avoided.
Does shotgun rib width vary by gauge?
It can. A shotgun model offered in 12, 20, 28 or .410 gauge may use different rib dimensions between gauges. However, gauge alone does not determine rib width. Always consider the exact model and barrel configuration in addition to gauge.
Can I use a 3/8-inch shotgun sight on a 5/16-inch rib?
Only if the sight is specifically designed to accommodate that difference through its mounting system or specified fit range. A sight designed for a 3/8-inch rib should not be forced onto a 5/16-inch rib. An incorrect fit can allow movement under recoil or damage the rib or mounting hardware.
Will a shotgun sight fit any ventilated rib?
No. "Ventilated rib" describes the general construction of the rib, not its dimensions. Vent ribs can vary considerably in width, thickness, profile and taper. A rib-mounted sight must be compatible with both the rib's width and the sight's mounting design.
What is the difference between a ventilated rib and a solid rib?
A ventilated rib is raised above the barrel and typically has openings or slots underneath it, allowing air to circulate and reducing heat transfer to the sighting surface. A solid rib is generally a continuous strip without ventilation openings. Rib-mounted sights are often designed specifically for one type or the other, so check the manufacturer's compatibility information before installation.
Why doesn't my shotgun rib measure the same as the listed rib width?
Published rib dimensions may refer to a particular point on a tapered or stepped rib, a specific model configuration, or a nominal dimension rather than a measurement of your individual firearm. Production changes can also result in different dimensions over a model's lifespan. If your measurement differs significantly from a published value, verify the exact model, gauge and configuration before purchasing a sight.
Can changing a rib-mounted shotgun sight affect point of impact?
Yes. Changing the height or position of a shotgun sight can change the relationship between your eye, the sight and the bore, which can affect point of impact when the shotgun is deliberately aimed. After installing a new sight, pattern the shotgun with the ammunition and choke you intend to use and confirm that the point of impact is where you expect it to be.