Gunsmithing Torque Wrench: All of the Settings & Uses

A torque wrench is a handy tool on the gunsmith’s bench and tackles many jobs. However, they are mainly used to mount scopes properly and consistently torque action screws.

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What is Torque?

Before diving into torque wrenches, let’s get a basic understanding of what torque is.

Torque is defined as the measure of a force’s tendency to produce torsion or rotation about an axis, equal to the product of the force vector and the radius vector from the axis of rotation to the point of application of the force; the moment of a force.

Put simply, it is how tight your screws are, or barrel nut is. There are many different formulas out there to calculate the amount of torque a screw can take based on a screw size, pitch, and material. However, none of that is essential for this discussion, as we are more worried about over-torquing and repeatability.

What to Look for in a Torque Wrench

The standard torque wrenches used by your local auto mechanic are not the same as what you need when working on firearms. You need a wrench that is adjustable down to the inch-lb for general work and one that measures in ft-lbs for barrel work. You will want the wrench to cover between 15-65 in-lbs of torque for general work. That will cover most of the scope mountings and action screw settings that you will use.

The ft-lbs torque wrench is only for torquing on barrels and barrel nuts, like on the AR-15. An automotive-type will work here as they also tend to measure in ft-lbs. Most AR Armorer’s wrenches like this one made by Magpul will have a 1/2″ square drive for use with a torque wrench. It is recommended that the AR barrel nut be torqued to 30 ft-lbs; however, this torque will be dictated by the alignment of the slots for the gas tube.

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Ideally, you want a torque wrench that accepts 1/4″ hex bits, as these are the most common type of screwdriver bit used in gunsmithing. This will allow you to use the proper fitting bit for every application, reducing the chance of marring up a screw.

Uses on the Gunsmith’s Bench

The uses of a torque wrench on the gunsmith’s bench are numerous. Most people will find them paying for themselves when used for mounting scope bases and rings. While they are not inexpensive, a stripped-out scope ring or receiver isn’t cheap either. The screws used for mounting scopes are generally pretty small and have a fine thread that is easily stripped out. The potential problem multiplies when aluminum is involved.

The first time you use a torque wrench when mounting rings and bases on a rifle, you will realize you have been overtightening them up to that point.

A torque wrench is also very useful when getting the most accuracy out of a rifle platform. Most rifles tend to have a sweet spot when it comes to the torque setting of their action screws. While it may not have a severe impact on your accuracy, if your rifle is adequately bedded with pillars, it won’t hurt. After all, accuracy is consistency, consistency down to action screw torque. I have personally tested this and have found the results to be shocking. You can read the full text below.

Action Screw Torque: The Pursuit of Rimfire Accuracy Part Three

Lastly, a torque wrench is only designed to be used one way. That means it should never be used to loosen or remove a screw. This can damage the wrench and cause a lot of issues down the road.

Applicable Torque Settings

The torque settings used below will give you a good guideline to go by. However, they may vary slightly depending on the manufacturer’s specs.

Screw Size	Common Uses	Torque (Inch-lbs)
6-32	Scope Base Mounts	18-20
6-40	Scope Base Mounts	18-20
6-48	Scope Base Mounts	18-20
8-32	Scope Rings	28-30
8-36	Scope Rings	28-30
8-40	Scope rings	28-30
10-24	Scope Base Windage Screws	40-45
10-32	Scope Base Windage Screws	40-45

These settings are suggestions based on using a lubricated screw; unlubricated screws require more torque to maintain consistency. A light coat of oil or Loctite is considered lubricated.

The guys over at the precision rifle blog are a good reference for action screw torque based on the action type. That article is located here.

Torque Wrench Storage

Torque wrenches use an internal spring to apply the correct pressure on each use. Therefore, they should always be stored at the lowest value to relieve that spring pressure. This will save on the wear and tear of the tool and make it last a long time.

The One You Need

Wheeler FAT Wrench – 59.95

This torque wrench is the only one that I have experience with. It has performed very well for me so far, and I have no reason to try another one. The handle has an excellent grip and keeps your hands from slipping even when they are covered in Hoppe’s.