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maximus otter

The importance of stock bolt torque

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Having become dissatisfied with the stock trigger on my Sako Finnfire Varmint, I ordered one of Baldie's replacement trigger springs for many Tikka and Sako rifles. At £5 delivered, I didn't have much to lose.

On its arrival I unscrewed the action from the stock, removed the trigger mech housing and replaced the spring. It probably only took slightly longer than typing these words has. Unfortunately I don't have a trigger pull weight gauge, so I have no before/after numbers for you.

A few days later I was off to the range to try out the new arrangement.

I fired two groups off a concrete bench, using a bipod and back bag, at 50 meters. Not only were they much larger than previously, but group centre had shifted down and to the left.

I was scratching my head and trying to work out why a lighter trigger pull would have this effect, when one of the other members - a high-level .22 LR target competitor - put me out of my misery: "You had to remove and replace the bolts securing the action to the stock, didn't you? Try giving them an extra ¼ turn with the screwdriver."

I found that one was fully tight, but that the other would screw in another few degrees.

The result? (Ignore the bottom 2 groups):

 

TargetSakoFinnfirestockboltstightenedcir

 

More evidence:

I left the bolts as they were on retightening them after having fitted the new trigger spring, and fired two groups (the "orange" ones).

I then thought, "If tight is good, surely tighter must be better?", and screwed them in as hard as I could with a manual screwdriver. The result was the red groups:

 

SakoFinnfiretargetsstockboltstightovalst

 

So I backed off the screws approximately 1/8th of a turn, and achieved the green groups:

 

SakoFinnfiretargetsstockboltstightovalst

 

I definitely need a torque wrench.

(Ignore the unmarked group, it was fired with a different brand of ammo. 'Scope was adjusted between some groups. The .44 holes weren't mine).

 

maximus otter

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I never realised how important something as simple as stock bolt torque was. Thanks for sharing your experience. It is a definite eye-opener. :)

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Very interesting, especially as you have the visual proof for us to see the variations

 

I wonder what range torque wrench would be best and what is the most cost efficient option!

 

MArk

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Very interesting, especially as you have the visual proof for us to see the variations

 

I wonder what range torque wrench would be best and what is the most cost efficient option!

 

MArk

 

I fancy the Borka, but - of course - there's no reliable UK source...

 

 

m.o.

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I had an issue at one point with a rifle and bedding. taylor who fixed it for me replaced the action bolts with Allen headed bolts which are much easier to keep tight.

 

Regards

 

JCS

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Definitely worth using a torque wrench for consistency.

I had a Savage Ftr for a while. If all 3 screws were torqued the same, accuracy was dreadful, slacken the middle screw and groups became tight again.

I will say that a proper pillar bedding job or a stock with integral bedding block should mean that torquing is far less critical.

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Very interesting, especially as you have the visual proof for us to see the variations

 

I wonder what range torque wrench would be best and what is the most cost efficient option!

 

MArk

Hi Mark I've had a few off the bay, Britool 0-50inch pounds and a Torqueleader 0-25inchPounds. Stupidly I sold a torque leader which went higher, thinking I'd have no use for it. Stupid boy.

Neil

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Thanks - it is worthwhile to actually see the difference achievable on what is recognised as a pretty accurate factory rifle.

 

Rgds

 

Ian

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So what is the proper torque values tightening then or is it a suck it and see job

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Posted 30 July 2013 - 10:39 AM

 

It's so nice to see someone else taking time to sort a 22lr.

Sometimes though, the problem is the rifle...as I found out.

 

I recently got a second hand Sako Varmint Finnfire. I got it unseen since the asking price was only £450 and the stock looked in good shape from the photo. The barrel had been hacked off to 14 inches by some Muppet, but since the only other example offered was £600 I thought it worth a punt. I knew I could always re-barrel if it turned out to be a dog. I also picked up an A-Tec cmm4 moderator.

 

Anyway, the rifle was as I thought with damage to the bore by indifferent cleaning rod use, revealed all to clearly by the bore scope, but the crown looked ok. The wood was in very nice shape.

 

I tested Win HP sub-sonic CCI segmented, Eley Club, Eley Tenex, RWS R50, RWS sub-sonic HP and Eley HP. Target ammo shoots well and was sub-sonic. The bullets are a bit harder than HP, so I thought I'd leave them for 100+ yd/plinking etc. The results of the hunting ammo were mediocre at best...definitely sub 50yd use.

 

I thought I'd try tuning the rifle since I had nothing to lose. I stripped the rifle completely and replaced the trigger spring with one from Baldie and set it to a tad over 1lb. I changed out the action screws for hex drive heads and I also replaced the worn out firing pin spring since it barely made an indentation in the cases.

 

I started with tuning the action screw torque. I fired a five round group at each torque setting going up in 5inlbs from 20-35inlbs That made a vast difference, the rifle liked 30inlbs. I then tuned the barrel with the moderator. I did this by dropping out one segment of the moderator at a time then shooting a group. After several test groups I decided on one segment out and a group size reduced by 50% . There seems to be no discernable difference to the muzzle report using the mark one ear, until you get down to one segment remaining.

 

I then re-fired the test groups with the hunting ammo. These are the results at 50yds, The CCI dropped a round that opened up the first group to 1.624 and 1.11 with Winchester. The QC from CCI/Win is poor IMHO. I am pleased I didn't give up. I use On Target to measure the groups.

 

[/url]">http://<a class='bbc...3bb4.jpg.html'>P1010219_zpsbe413bb4.jpg

 

I have since had Neil Mckillop install some pillars. This has shown yet more consistency and smaller groups. I have yet to run a proper re-test but indications are promising. I have also sorted the ammo by rim thickness. This does wonders for long range group size and consistency, again I have not re run this test due time, but it seems flyers become a rare event from the several groups I have fired so far. I am now awaiting the new 18inch barrel from Lilja.

 

ATB

 

I agree regarding torque settings. I posted the above last year.

 

ATB

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This is very interesting, but what about the Ruger 10/22 which only has one bolt holding the action to the stock?

I have made an attempt to devcon my action to the stock and it's now currently solid as s rock. I do need to work on the trigger and do some serious testing but can anyone offer torque setting advice or is it all down to testing going up in torque increments?

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I ran a VQ semi for around 8yrs or so.

 

They work well with match ammo but I could not match a quality BA rifle accuracy from it. (Think Anschutz)

 

I tested every brand of ammo I could get my hands on and lets be frank, I live 30 minutes or so from the NSRA and the choice was huge. I found no impact with accuracy by varying the torque with my VQ. It had the rubberizes Hogue stock. The build up of lead shaving and crud around the breech area trends to make a mockery of headspace etc. and from what I've seen, that has far more effect on group size in the VQ than the bedding screw.

 

ATB

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