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How tight must the stock and scope screws on my gun be?

A reader wants to know what's best for accuracy

stock bolt tightening

Q: I have been told that I need to keep my stock and scope screws at the correct torque setting for best accuracy. What is this and how do I achieve it?

A: Tightening rifle and scope screws to hold or grip an item securely can greatly influence the way a rifle performs. To maintain correct tension on the screws, I use the Brock and Norris adjustable torque driver. The simple tool uses the standard 1/4in hex bits used in most power tools at home.

  1. Separate the two pieces of the hex tool holder and locate one of the six available holes in the torque driver handle. Each represents 25, 30, 35, 
40, 45 or 50in/lb settings.
  2. Decide on the torque setting 
for your rifle. For example, you need 
15lb-20lb for scope screws, so use 
the 25lb setting or 30lb torque for 
scope bases. For rifle stock screws 
in a wood or fibreglass stock use 40lb or up to 50lb for bedded stocks with synthetic materials (aluminium requires less torque).
  3. Place the hex bit in the 
screw you are tightening and hold 
the torque driver only by the grey handle. When the desired torque setting is reached the handle disengages and rotates 90° so no 
more force is exerted and the exact torque setting is reached.
measuring length of pull

Stock length of your rifle must be right for your physique

Q: Is there a good reason to torque set my rifle’s stock and scope screws, as with a car or motorbike?

A:  Yes, very much so. With rifle shooting it is all about consistency. Having the rifle perform the same 
way every time greatly contributes 
to your accuracy.

The stock and scope are ‘attached’
to the barrel and action, as it were, so they have to be securely and precisely fitted. This means it is essential that 
the screws be set at the correct tightness or torque. You can own the best and most expensive rifle and mount the latest scope, but if you fail to tighten 
the stock screws or scope mounts 
correctly, you may not achieve your rifle’s potential. A loose screw will 
cause inconsistencies and it can 
be dangerous. It can damage your 
rifle, too.

One area that is often overlooked 
is how tight — or loose — you secure the stock to the rifle’s metal work. This applies to all types of rifle, whether bedded directly to the wood, or with 
an artificial bedding compound.

An inexpensive torque tool, such as a Fat Wrench from Norman Clark Gunsmiths, is a simple cure to accurately tighten all your firearm’s screws. The recommended torque settings for wood or fibreglass stocks without pillar bedding is 40in/lb. 
With pillar bedding it is 65in/lb. My advice is to experiment with different settings to achieve the best accuracy.

Scope mounting screws should be set at 15in/lb to 20in/lb for steel rings, while aluminium ones need only 10in/lb to 15in/lb. Base mounts should be tightened to 30in/lb.