Standard Scope Mount Screw Sizes: Know The Basics

The size of a standard scope mount screw varies depending on the rifle model and manufacturer. The most common sizes are #6-48 and #8-40 screws. #6-48 screws have a diameter of approximately 0.138 inches (3.5 mm), while #8-40 screws are larger with a diameter of approximately 0.164 inches (4.17 mm). Some rifle manufacturers, such as Savage and Remington, have transitioned from using #6-48 to #8-40 screws in certain models, citing increased strength and durability. It is important for rifle owners to be aware of the specific screw size required for their rifle model to ensure proper fit and function when mounting scopes or other accessories.

Savage rifles use #6-48 or #8-40 screws

The standard scope mount screw size depends on the make and model of the rifle. Savage rifles, for example, have used both #6-48 and #8-40 screws.

#6-48 screws were the standard size for rifle scope mounts for decades, and many bolt-action rifles, including Remington, Winchester, and Savage, typically used these screws to attach a scope base. A #6 screw is approximately 0.138 inches in diameter, and the corresponding hole size for #6-48 screws is 0.120 inches.

However, starting in 2020, Savage transitioned to using #8-40 screws in certain models of their rifles, including the Savage Model 110 and Axis. #8-40 screws are larger and stronger than #6-48 screws, with a diameter of approximately 0.164 inches.

It is important to note that the change from #6-48 to #8-40 screws in Savage rifles is not just a matter of replacing the screws. The transition requires purchasing a compatible scope mount for the specific screw size to ensure a proper fit and function.

To determine the screw size on a Savage rifle before purchasing a scope mount, there are a few methods:

• Hex Key Fit Test: Insert a 1/8" hex wrench into the screw holes on the receiver. If it fits snugly, the screw hole size is #8-40. If it doesn't fit at all, the size is #6-48.
• Measure the Screws: Use a pair of calipers to measure the screws. Screws measuring approximately 3.5 mm (0.138 inches) indicate a #6-48 screw hole size, while screws measuring approximately 4.17 mm (0.164 inches) indicate a #8-40 screw hole size.
• Identifier on Savage Rifles: Savage centerfire rifles manufactured in 2021 or later with #8-40 screw holes will have an identifier on the bolt handle slot. For the Model 110, this identifier is located on the top of the receiver. For Axis models, the newer #8-40 screw holes will appear completely round when viewed from the rear of the receiver, lacking the flat cuts found on older models.
• Serial Number: Savage Axis Rifles with serial numbers higher than N936371 are drilled and tapped for #8-40 screws.

By using these methods, Savage rifle owners can identify the screw size of their rifle and ensure they purchase the correct scope mount for a secure and functional setup.

#6-48 is standard for Remington 700 rifles

#6-48 screws are commonly used for mounting scopes on rifles. While there are different screw sizes available for scope mounts, #6-48 is the standard size for Remington 700 rifles. This screw size has been the industry standard for decades, used by various rifle manufacturers, including Remington, Winchester, and Savage.

When purchasing a scope mount for your Remington 700, it is crucial to ensure compatibility with #6-48 screws. Some scope mounts are designed specifically for this screw size, while others may require a different size, such as #8-40. It is always recommended to verify the screw size required for your rifle model before purchasing any accessories or scope mounts.

The #6-48 screw size is identified by measuring the screw hole or using a hex key fit test. The screw hole size for #6-48 is approximately 3.5 mm or 0.138 inches, while a 1/8" hex wrench that fits snugly indicates an #8-40 screw hole size.

Additionally, when shopping for scope mounts, pay attention to the specific model and type of your Remington 700 rifle, as there may be variations in screw sizes among different models. It is always best to consult reliable sources and seek advice from experts or manufacturers when in doubt.

By ensuring that you have the correct screw size and compatible scope mount, you can securely and safely attach a scope to your Remington 700 rifle, enhancing your shooting experience and accuracy.

#8-40 is larger and stronger

When it comes to scope mount screw sizes, the specific measurements can vary depending on the firearm in question. However, it's important to note that the #8-40 screw size is larger and stronger compared to other options like #6-48. This size difference is not just a simple matter of replacing screws, as it requires compatible scope mounts to ensure proper fit and function.

The #8-40 screw size offers a bump in fastener diameter compared to the standard #6-48 size. This larger diameter provides increased strength and durability, making it a popular choice for certain firearm models. To identify if your rifle uses #8-40 screws, you can perform a hex key fit test by inserting a 1/8" hex wrench into the screw holes on the receiver. If the hex key fits snugly, it indicates a #8-40 screw hole size. Additionally, direct measurement with calipers can be used to distinguish between #6-48 and #8-40 screws.

The change from #6-48 to #8-40 screws has been observed in some rifle models, such as the Savage Model 110 and certain Remington rifles. For example, the Savage Model 110 Elite Precision Left Hand, 110 Precision Left Hand, and 110 Wolverine/110 Haymaker are known to use #8-40 screws. This change may cause confusion among users, so it's important to verify the screw size before purchasing or working on scope mounts.

The #8-40 screw size is also specified for mounting applications, ensuring perfect alignment with the receiver. This screw size is designed with a 45-degree taper under the head, which seats into a corresponding 45-degree counterbore. This feature guarantees 360-degree contact underneath the screw head, enhancing the stability and security of the mounting system.

In summary, #8-40 screws are larger and stronger than their #6-48 counterparts, offering increased fastener diameter and improved durability. This screw size is used in select rifle models and requires compatible scope mounts. Proper identification of the screw size is crucial to ensure the correct parts are used for a secure and functional setup.

#6-48 screws are 3.5mm or 0.138 inches

The #6-48 screw size has been the standard for decades for tens of millions of rifles. However, some manufacturers have started using larger screw sizes, such as #8-40, for added strength. It's important to note that simply replacing the screws with a larger size is not recommended, as it can affect the proper fit and function of the scope mount.

To ensure compatibility, scope mount purchases should match the specific screw size of the rifle. For example, the Savage Model 110 requires scope mounts that are compatible with either #6-48 or #8-40 screws, depending on the model year.

There are a few ways to determine the correct screw size for your rifle. One method is the Hex Key Fit Test, where you can use a 1/8" hex wrench to test the fit of the screw holes. If the hex key fits snugly, it indicates an 8-40 screw hole size, and if it doesn't fit at all, it means the hole size is 6-48. Another approach is to measure the screws directly with a pair of calipers.

In summary, #6-48 screws have a diameter of approximately 3.5mm or 0.138 inches, and they are commonly used for mounting scopes on rifles. However, it's important to verify the correct screw size for your specific rifle model to ensure compatibility and proper functionality.

#8-40 screws are 4.17mm or 0.164 inches

The size and type of screw used to attach a scope mount to a rifle are important considerations when selecting the appropriate scope mount for your firearm. It is crucial to ensure that the scope mount is compatible with the screw size of your rifle to guarantee a secure fit and optimal functionality.

To identify the screw size, you can perform a hex key fit test or use calipers for measurement. The hex key fit test involves inserting a 1/8" hex wrench into the screw holes on the receiver. If it fits snugly, it indicates a #8-40 screw hole size. Alternatively, calipers can be used to measure the screws directly, with #8-40 screws measuring approximately 4.17mm or 0.164 inches in diameter.

It is worth noting that #8-40 screws are larger and stronger than the commonly used #6-48 screws. The change from #6-48 to #8-40 screws in certain rifle models may cause confusion among users, so it is important to verify the screw size before purchasing or installing a scope mount.

Additionally, some rifle models may have identifiers or specific serial numbers that indicate the use of #8-40 screws. These details can be helpful in determining the correct screw size for your rifle.

Frequently asked questions