Torque Specifications

[Faster Daddy!]

I am looking for a range of torque specifications I can experiment with for actions that are bedded on aluminum pillars. Any suggestions? Two Winchesters Model 70's, one in 300 WSM and one in 270 WSM. Also, one Remington 700 in 204 Ruger. Thanks.

 

[sendero72]

Don't know about the Winchesters, but the Remington is based on the type of stock. Wooden stocks are 35 inch lbs, fiberglass are 45. Remington has it posted on the website, please check or just call them. My sendero has a HS Precision which is 65 inch lbs.

 

[ICANHITHIMMAN]

I use 65 inch pounds on my HS precision but its really just a bench mark and they are not pillars. I would start some where around 40 and go up and down just to see what it does to your groups.

 

[Outlaw6.0]

I use 65 inch pounds on my HS precision but its really just a bench mark and they are not pillars. I would start some where around 40 and go up and down just to see what it does to your groups.

^^^ This is sound advice. From my lowly .204 to my 338RUM. From unbedded wood stocks to a solid aluminum chassis, NONE of my action screws exceed 40in/lb. IIRC with a 1/4in fastener the clamping force is somewhere in the 1200lb range. An ex-USMC armorer has reported seeing eventua stud yield at 65in/lb leading to loss of accuracy. Now, That is definitely an extreme case, but from what little i've read, 65 may be a little too high for that small of a fastener.


YMMV

 

[Timber338]

^^^ IIRC with a 1/4in fastener the clamping force is somewhere in the 1200lb range.
YMMV

You guys can estimate fastener preload (clamping force from the action screws) very easily with the following equation. (assumes lightly lubricated threads)

Preload Force = Torque / (0.21 * bolt diameter)

Where Torque is in inch*lbf, 0.21 is the unitless coefficient of friction, and bolt diameter is in inches. You can re-arrange the equation and input your desired Preload Force and calculate your necessary Torque if you prefer it that way too

So for a 1/4-28 action bolt (0.25 inches diameter) and 65 in*lbf Torque, the preload force = 1238 lbf.

Outlaw 6.0 is right on... And I agree that is a high preload. 45 in*lb torque still gives 857 lbf of preload for each action bolt.

And remember these are estimates... lots of variables can change the actual preload force, but gives you a good starting point.

 

[J E Custom]

Do a search on "torque Recommendations" and you will find all of the recomended Torques.

J E CUSTOM

 

[Faster Daddy!]

Thanks guys, I really appreciate it!

 

[Joaquin B]

I am looking for a range of torque specifications I can experiment with for actions that are bedded on aluminum pillars. Any suggestions? Two Winchesters Model 70's, one in 300 WSM and one in 270 WSM. Also, one Remington 700 in 204 Ruger. Thanks.

I don't remember where, but I read an article about tuning the rifle's action screws to optimize accuracy, so I first started playing with my Tikka 595 in .260 Remington. I replaced the slot head screws with hex socket type and shot a series of 3-shot groups at 300 meters, with the first group being at 5.5 N-m (Gehmann metric tourque Wrench) and discovered that at a setting of 6.5 N-m, the group was smallest. I repeated the test with similar results and settled on 6.5 N-M.

Did the same with my Winchester M-70 fitted with a 30-06 varmint weight fluted, 24 in. barrel and found 6 N-m worked best in my rifle. Same for my Sako AII.

I hope this info. helps.