questions about the newer 2 action screw Accustocks

[Petermari]

Has anyone noticed a change in accuracy after removing the action from the Accustock? I've googled quite a bit but can't really find a consensus. I thought I'd ask Accustock owners about their first hand experience with this issue. To adjust the Accutrigger, the Accustock needs to be removed. Even a simple trigger cleaning means removing the Accustock. The accuracy issue seems to come from the action screw torque. Assuming they are torqued at 45# at the factory. I read a post somewhere about the retorquing procedure and it seems pretty straight forward. Front screw, rear screw in increments until you reach 45#. I'd really like to lighten my Accutrigger pull but I don't want to do it and find that the rifle doesn't shoot as well after putting the Accustock back on. Comments welcome.

[missed]

I have not, I have had my actions out of the stocks multiple times with no difference. I just torque back down to 40"# and I'm good to go.

[Petermari]

Thanks. That's reassuring. Are you using 40'# instead of 45"#.

[Petermari]

Sorry. Meant "#'s not '#'s.

[missed]

Yeah I'm just running 40" my guns are happy at that, but I do know others that have found a happy number that is other than those numbers.

[Starosta]

Hey, guys, this is exactly what I was playing with last Saturday :-)
Sorry for the post length.


TRIGGER:
I've adjusted the trigger as low as possible and there's been no bump/slam-fire yet.
(Just for you guys who are stuck in "should I adjust it or not" as I've been for a while...)


STOCK TORQUE:
Past few days I googled a lot and found two sources of interesting information:
[1] http://www.accurateshooter.com/technical-articles/savage-action-screw-torque-tuning/
[2] http://forum.snipershide.com/snipers-hide-bolt-action-rifles/39539-torque-accustock.html

EQUIPMENT etc:
I have a Savage 10TR (308Win in AccuStock) with 20" barrel and cheap muzzle brake. Factory ammo - Sako 168gr HPBT Sierra RaceHead.
I shot 4-rounds groups adapted to 4-rounds magazines. I let the barrel cool down before shooting another group whenever I couldn't keep my hand on the barrel easily.
Also used mounted harris bipod and sock shooting from prone position on a 100 metres distance.

For particular torque description I used values in lb.ft, set by a (brand new) F.A.T. wrench.
As a "front screw" I mean the screw just in front of the magazine release, as a "back screw" I mean the screw UNDER the bolt release.
I use the format "30/10" meaning front screw torqued to 30lb.ft and back screw torqued to 10lb.ft...

DISCLAIMER:
Let me state that I don't claim this method nor results as the right one ;)
I just tried with my setup - and there was for sure a plenty of room for shooter's error - obviously your mileage can vary.
But enough chatter...


First, I tried something similar to the
METHOD [1]:

Beginning with action seated into stock carefully and having the lug "bumped" against the stock a little, both screws were torqued to 10/10. Then I tightened front screw to 30/10.
I tried a few groups with various torque settings of the back screw: 30/10, 30/15, 30/20, 30/25, up to 30/30.
As this was the first (wide) comparison of torque settings effect on accuracy, I tried only 2 groups on each settings. (Eventually 4 groups when I was uncertain about my shooting.)

See the groups below (column on the right excluded, that one belongs to method [2]) ;)
http://imageshack.us/scaled/large/607/q4pw.jpg (http://imageshack.us/photo/my-images/607/q4pw.jpg/)

http://imageshack.us/scaled/large/4/m2z1.jpg (http://imageshack.us/photo/my-images/4/m2z1.jpg/)


The second test method I used was alike linked
METHOD [2]:

I loosened both screws, "bumped lug" and started to tighten both screws as equally as possible (in 5lb.ft increments at most).
Unfortunately these are only 3 or 4 groups as I wasn't amazed by the results.
I used "30/30~" format for description and went with 30/30~, 35/35~ and 40/40~ settings.

You can see the results above in the right column.


In the end, I came back to 30/30~ settings which I tested a few more - but I am not sure if the average results (0.6-0.9MOA) weren't caused by my fault (getting dark, having tired eyes and shouldered already 60+ rounds which I am not used to).

You can see the results below:
http://imageshack.us/scaled/large/820/fz9c.jpg (http://imageshack.us/photo/my-images/820/fz9c.jpg/)


CONCLUSION?

IMHO it DOES matter in case you're trying to achieve best possible accuracy. (Almost all groups under 1MOA anyway - does it matter for you might be the question.)
I'll try to find my sweet spot between 25/25~ and 30/25 which seemed to be the best.

You have to try for yourself with your rig, I suppose different ammo, brake or barrel length could significantly matter.
If I were you, having AccuStock re-assebled after trigger adjustment - I would start with 30/20, 30/25, 30/30 settings.

Hope this helps anyway.
The test was very demanding on shooter's concentration and abilities (and I am no great shooter at all).


Feel free to comment and share your own results! ;)

[Petermari]

Starosta. Thanks for reply. Good stuff. I think I'm leaning toward the camp that believes that action screw torque deserves a better look. For example. How did Savage come up with the 45"# number? One rifle? Surely they tested torque values and had some reason for the 45"# number. Maybe not. Perhaps I'm just overthinking this stuff.

[J.Baker]

Unfortunately the above testing reveals little because it wasn't shot from a gun vise and thus shooter error wasn't 100% removed from the equation. It does however show what those of us who have done this experiment before already knew - that the ft-lbs the action screws are torqued to really isn't as important as using the same amount each and every time. The reason for this (and if you scroll back up and look at the targets it's obvious) is because changing the torque will have a small effect on the POI. The group sizes really didn't change much at all, but where the group is on the target clearly dances around the dot as the torque value changes.

[Neo2savage]

Torque values are generally established by reviewing engineering tables that describe the failure modulus of various fastener sizes and materials. Savage could have some really sharp engineers that look at factors other than the book failure values. If so, that would be extremely impressive.

[sharpshooter]

Looks like a waste of 82 bullets if you ask me. Anytime that different torque produces different results, there is a problem of stress in the mix. The point of the accustock was to provide 3 point bedding by actually pinching the receiver on the sides and pulling down to bottom.It is evident that this type of securement is not consistent. While the accustock is stiffer than it's predecessor, the good ole tupperware version, is has shown to actually induce more stress than even a wood stock. When everything is right, the torque has no effect on accuracy.

[Starosta]

Thanks for opinions.

I bet there would be much more relevant results if the shots were fired by F-class shooter, from the bench, with hand loaded ammo, without wind and checking the speed of every bullet.

Of course I cannot expect consistent groups of 0.25moa with the stuff.
Thats why I'd be interested in your results - with your rifles.

[foxx]

Thanks for opinions.

I bet there would be much more relevant results if the shots were fired by F-class shooter, from the bench, with hand loaded ammo, without wind and checking the speed of every bullet.

Of course I cannot expect consistent groups of 0.25moa with the stuff.
Thats why I'd be interested in your results - with your rifles.

I don't think JBaker is questioning your shooting ability. I think he saying your hypothesis cannot be tested reliably by anyone not using a vise, (due to human error) and that that there are other, more fundamental points demonstrated by your test. (Different torque seems to affect POI more than group size). Sharpshhoter concludes that the Accustock is an imperfect improvement over Savage's ordinary factory stock. (It introduces other fundamental problems relating to accuracy). If I dare relate what I have read elsewhere, and discovered thru my own, albeit limited, experience: gradual, CONSISTENT torqueing of the screws in a particular sequence will bring the most out of the system. Each rifle may have its own "likes".

Of course, I am no expert on Accustocks, just a somewhat frustrated and mildly dissappointed owner of some.

[Starosta]

foxx: I didn't take it wrong or personaly in any way.
I just think the shooter's error is a big deal - which is also what you guys said.

From what I know about my shooting:
The POI is caused both by torque change and shooters error (and wind). As I am a mediocre shooter and bigbore begginer, I am focused especially on keeping the groups tight when in position.
But - as a barrel cooldown and torque changes requires position change - this also affects my POI because of yet missing the skill of true consistency.
The other part played wind which I just didn't fight against and tried only to wait for same wind blow in one group.

Long story short: you guys're right, there is some POI shift, but not as much as one would say from the targets.
I just didn't care about it at all.
That's why I mentioned F-class shooter and a tunnel. And of course, the ammunition.

[Brent]

I have close to 800 rounds down the tube of my 116 6.5-284 and don't like pulling the stock off unless I have to. I worry about potential loss of accurace as well but have no proof one way or the other how it is affected by torque alone. I put 45" on my screws as well and left it there. The rifle shoots fine. I tend to shoot .5 MOA out to 1300 yards consistently.

It would probably be worth a little effort to take a known good load and try a few different settings to see if actual group size changed.