Gun Screw Sizes: The Most Common You'll Encounter

Gun owners and firearms enthusiasts will inevitably need to familiarize themselves with the various fasteners, screws, and their sizes, in order to keep their weapons in good condition. While the specific screw types and sizes can vary depending on the gun's make and model, there are some standard screw sizes and types that are commonly used in the world of firearms. These include socket head hex, socket head Torx, flat head, button head hex, set screws, and pan head Phillips, among others. Proper torque application is essential to ensure the gun's functionality and safety, and gun owners should refer to manufacturer guidelines or seek professional gunsmithing services for specific instructions.

Fillister Head (Type A)

The following are some examples of Fillister Head (Type A) screw sizes:

• #3-48 X 1/8"
• #3-48 X 1/4"
• #5-40 X 1/4"
• #5-40 X 3/4"
• #6-32 X 3/4"
• #6-40 X 5/16"
• #6-48 X 3/16"
• #8-40 X 1/4"
• 1/4"-20 X 1/2"

These screws can be found in various finishes, including brass with a nickel finish, black oxide, and stainless steel.

Headless Plug Screw (Type C)

The Headless Plug Screw (Type C) is a type of gun screw used in firearms and accessories. It is one of the most common screw types, along with the Fillister Head (Type A). These screws are typically made from an alloy steel with a black-oxide finish, giving them a subtle appearance and mild corrosion resistance.

Type C headless plug screws come in a variety of sizes, with different thread lengths and head diameters. The thread length of a screw is measured under the screw head. The head diameter, or "head O.D.", is the size of the screw head's outer diameter. For example, a Type C headless plug screw with a thread length of 1/8" can have a head O.D. of 0.200" or 0.240".

When selecting a headless plug screw, it is important to consider the specific application and torque requirements. Gun screws are typically tightened to a predetermined torque value to ensure sufficient clamping force and secure the connection. The screw's diameter, thread pitch, material, and application can all influence the specified torque value.

It is also worth noting that gun screws may have different drive styles, such as slotted, Hex, Philips, or Torx. Therefore, it is important to use the correct tools and screws when working on firearms to ensure a proper and secure fit.

By following the appropriate guidelines and selecting the right Type C headless plug screw, individuals can ensure the safe and proper assembly of their firearms or accessories.

Socket head hex

When selecting socket head hex screws, it is important to consider the appropriate size and material for the specific application. The size of the screw is determined by the thread pitch and the head type, with the thread pitch measured in inches or millimetres. The most common sizes for gun screws are #6, #8, and #10, which correspond to specific fractions of an inch.

In terms of material, steel is the most common option for socket head hex screws, offering robustness and durability. Stainless steel is also popular due to its higher corrosion resistance, while brass is often used in electrical components and marine applications for its electrical conductivity and non-magnetic properties.

To ensure proper installation and maintenance of socket head hex screws, it is recommended to follow manufacturer guidelines for torque values and to use high-quality tools that fit snugly to avoid damaging the fasteners. Additionally, threadlockers can be used for critical applications to provide extra security.

Flat head

Flat-head screws are a type of fastener characterised by a flat or horizontal drive head, which includes a slot or Phillips drive feature. Flat-head screws are often used for firearm accessories, while socket head capscrews are typically used for action screws and optic mount screws.

Flat-head screwdrivers come in a variety of sizes and lengths, with the length of the shaft and the width and thickness of the driver being the key measurements. Flat-head screwdrivers range in size from millimetres to bigger fractions of an inch. The width of the driver head is represented by the first number, while the second number indicates the shaft length. For example, a flat-head screwdriver size of 3/32 by 1 1/2 indicates a driver head width of 3/32 of an inch and a shaft length of 1 1/2 inches.

When selecting a flat-head screwdriver, it is important to choose one that fits snugly into the slot of the screw. A screw with a head that is 1/4-inch wide, for instance, would not be easily turned by a driver only half as wide. Similarly, the thickness of the slot on the screw head should be matched by the thickness of the screwdriver for optimal results.

Flat-head screwdrivers are available individually or as part of a set. A set typically includes a range of driver sizes, from short to long shafts, allowing for versatility when working with screws in tight spaces or those that are more accessible.

Set screw

The Pachmayr 03054 277-piece firearm screw kit is a popular option for gunsmiths and firearm owners. It contains 12 each of 23 different types of screws, including fillister head, oval head, and plug screws in various lengths and threads. The kit also includes tweezers for easy selection and a 24-compartment plastic case for storage.

Another option is the Forster Products gun screw assortment, which includes 12 each of their 23 most popular screw sizes, heat-treated and blued. This kit offers a cost-effective way to ensure you have the right screws when you need them.

When selecting screws for gunsmithing, it's important to consider the thread pitch, head type, and finish or material. The thread pitch is typically represented by two hyphenated numbers, with the first number indicating the major diameter of the threads and the second number indicating the number of threads per inch. Head types for gun screws can vary, including socket or button-head cap screws and flat-head screws. The finish is usually a black-oxide alloy steel to give a subdued look and mild corrosion resistance.

By following these guidelines and selecting the appropriate set screws, you can ensure that your firearms are securely assembled and maintained.

Frequently asked questions