A reader wants to know what's best for accuracy

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.

Norman Clark Gunsmiths also 
sells the Wheeler torque setter, 
which is a more typical ratchet-
type torque wrench.

Our shooting technical expert Mike George adds his thoughts on torque setting:

In the days when I performed all the new gun tests for Sporting Gun, I always reckoned that Miroku employed a retired sumo wrestler as their stock-bolt fitter.

In practice, the bolt needs only be tightened sufficiently to prevent its shaking loose during prolonged shooting. So how tight is that?

I have only ever seen one recommendation, and that was in the instruction book for an American-built Ruger. Ruger said the ideal was 6ft/lb of torque, which is the equivalent of 6lb of pressure on the end of a lever a foot long.

In engineering terms, that isn’’t very much. You tighten the wheel nuts on your car to 10 times that!