Springers – Screw Torque

I’ve had a bit of a springer revelation this week. I’d taken the Prosport out in the rain last Sunday. So that night I took the action out of the stock to give it a dry and a clean. Putting it back together got me thinking…I’d never really considered the torque setting of the various stock screws (six in total on mine). Since I’ve had this gun there have been a few issues with shifting POI (point of impact), which I’ve not been able to trace.

What if different torque settings are putting different amounts of tension around the stock? Then the recoil might be shifting that tension over time, resulting in the scope zero wandering.

As always I asked my mate Google, and there were lots of results. This was promising. Plenty of these results were discussions on forums, with the general consensus that stopping the screws moving was very important for accuracy. Bingo!

So I dug out my smallest torque wrench and my blue loctite, determined to put this thing together properly for once. But what torque to use? I couldn’t find any specifications for the Prosport or the similar TX200. What I did find was the Weihrauch guidelines. I am fairly impatient in general, so this was good enough for me.

The numbers I found were :
Front stock = 2.5Nm
Large trigger screw = 5Nm
Small trigger screw = 2.5Nm

Annoyingly my smallest torque wrench is rated from 5-25Nm. It does go lower, but isn’t calibrated below 5Nm. I’ve gone ahead with this, but made a note to buy something smaller in the very near future.

The 4 forend screws went in (with a smear of blue loctite each). No problems. Then the large trigger guard screw. The wrench was set to 5Nm, but it  was getting much tighter than I would normally do. I felt a bit uncomfortable about this, so lowered it to 4Nm instead. 

In fact all of them felt tighter than I would normally do. In the past I have just used an alan key, with the long end in the screw and turning the short end. This makes me think that I have been under spec all this time….

With everything back together it was time to test. Although the main idea of this exercise was consistency, I thought an accuracy test was in order. And I was very happy with the results!

Each group was 5 shots, at 15 yards (my maximum garden distance) and laying prone. I know plenty of people would be expecting one hole groups at this distance, but these were on par with my best. (Remember I’m still a bit of a beginner to target shooting). 

So initial results are promising. Hopefully the zero holds and I’ll have a bit of luck at Kingsley this Sunday. My top HFT score so far is 42/60. My next goal is 45.

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4 Comments on "Springers – Screw Torque"

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Duncan Rogers
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Interesting stuff Dan.
regards, Duncan

Michiel
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Torque is expressed as Newton-meter (or an impractical imperial equivalent thereof). If you know the weight (in Newton) of your rifle, you can calculate the amount of ‘meter’ you’d need to get the right amount of torque.

If your rifle weights 5 kilograms, that would be about 50 Newton of gravitational force. You would need to hold an allen wrench 0.1 meter from the screw to get 5 Nm of torque.

Rich
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I think the only thing to add here is a warning on over tightening stock bolts and screws.
Depending on the materials involved you can easily strip the threads in the action.