Gunsmithing Torquing for tight group

[Long_Trang]

I recently had a pillar bed job done on my custom 300WM. I ordered stainless Rem 700 trigger guard screws (at the suggestion of my gunsmith) for a Rem 721 action. He told me to set the forward screw at 45" lbs and the rear at 30" lbs to start with. He also told me the maximum recommended torque is 45" front/35" rear; yet (he informed me) the military goes tighter. Doing what he said, I took it out and adjusted while firing to tighten up my groups. I kept the front set at 45" and adjusted the rear from 30" and up an inch/lb at a time per group. I found 32" lbs for the rear tightened up the groups a bit; and the best, however, I noticed the barrel was in contact with the stock as I couldn't slide a bill (where I was able to before). Having tightened up to 35, the free float has returned. My guess is the 32" lbs is a bit too loose and letting the barrel sag?
My questions are: 1)What is the safest maximum torque? I keep hearing others speaking of 60" lbs for some rifles. 2)Is the forward screw best left at maximum and adjust the rear one only? ...And if not,...3)What is the best procedure regarding adjusting both screws? Adjust one first until my groups tighten, then repeat with the other?
Thanks in advance.

 

[desertrat1979]

Re: Torquing for tight group

I was under the impression to do both the same. If the rifle is sitting correctly, equal pressure means no induced stress from one side pulling more than the other.

 

[LRI]

Re: Torquing for tight group

I have a friend in Seattle who makes a very, very good living designing fasteners for the aerospace industry.

He took the time once to research this subject for me based on a couple of different materials and thread pitches.

In a nutshell if you exceed 40inchlbs on a 1/4"-28 screw you are right at the threshold of the more common materials used for gun screws (300 series SS and 12L 17 steel) Exceeding the maximum tensile load means something has to give. Since most receivers are made from tool grade steel that's been heat treated its unlikely the internal threads will yield at 40inchlbs.

The path of least resistance. . .

If the rifle is truly pillar bedded and its done properly there's no reason to ever exceed this. Regardless of caliber, barrel length, receiver style, etc.

Good luck.

C

 

[PCR]

Re: Torquing for tight group

I use these torque settings:

Factory plastic or wooden stock with factory bottom metal = 45# front and back.

Composite/fiberglass stock with machined aluminum or steel/ bottom metal = 55# to 65# front and back.

 

[RADcustom]

Re: Torquing for tight group

It sounds like you did not receive a stress free bedding job.

 

[mdesign]

Re: Torquing for tight group

^^ was thinking the same thing. On my pillar bed jobs, the action/barrel does not move when the screws are tightened. As far as how tight to tighten...I've also heard 60 in/lbs but cannot say I can tell the difference from 45-60, my rifles shoot the same.

Always did kind of wonder if there was a science to this or not.

 

[Long_Trang]

Re: Torquing for tight group

Thanks for all the input. It is truly appreciated.

 

[Clark]

Re: Torquing for tight group

http://www.jamescalhoon.com/bedding.php

 

[TXHunter]

Re: Torquing for tight group

Simple test for stress free bedding - grab barrel in vise (make sure to use padded vise jaws) with stock upside down / place one hand lightly on barrel and stock at front of stock / slowly loosen front action screw with other hand / if you feel stock move any amount at all relative to the barrel at front of stock then there is stress on the action as a result of poor bedding. Of course this assumes a free floated barrel.

As for action screw torque, HS Precision has for years specified 65 in-lbs and they and many others sell t-handle torque wrenches set at 65 in-lbs. When we pillar and glass bed a stock, we torque the screws to the same 65 in-lbs. However, do not use anywhere near this much torque on any stock, wood or synthetic, unless it has a bedding block or pillars. i think Remington specs around 35-40 in-lbs so that you don't crush the wood or plastic on those type of stocks.

 

[TomS308]

Re: Torquing for tight group

http://savageaccuracy.com/2010/02/01/how-i-tune-a-savage-receiver/

 

[Alan Warner]

Re: Torquing for tight group

I agree with Chad. If it is bedded properly, torque is almost irrelavant. (Sp) I always run 40 Inch pounds but have found 35, or 45 or 50 yield the same results. If you find that screwing with torque settings make a change in your groups, your rifle is not bedded correctly. period.
I do torque the pillars when bedding a rifle prior to setting it in the glue.
Alan

 

[Graham]

Re: Torquing for tight group

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Old Eyes</div><div class="ubbcode-body">I agree with Chad. If it is bedded properly, torque is almost irrelavant. (Sp) I always run 40 Inch pounds but have found 35, or 45 or 50 yield the same results. If you find that screwing with torque settings make a change in your groups, your rifle is not bedded correctly. period.
I do torque the pillars when bedding a rifle prior to setting it in the glue.
Alan </div></div>There you go: 'couldn't have said it better.