Gunsmithing Torquing a barrel on receiver?

[pinzmann]

Is there a set torque in ft-lbs for torquing a barrel on a receiver? I thinking about having two barrels on a new build I'm planning and would like to be able to switch between them. Not real often but maybe a few times a year. Is it important to torque to the same value each time? Now when I build a rifle I use a fairly basic wrench to tighten the barrel, it has no ability to accept a torque wrench. All my actions are left-hand so that limits my options also.

 

[EXTREMEPREJUDICE]

Well, I use the Surgeon Action wrench on my switch barrel rifle and set to 40 ft/lbs. of course it has the square cut to accept the socket driver. On AR's I torque to 65 ft/lbs. and have never seen a barrel nut wrench that did not have the socket cutout. I am not a smith, works for me.......................YMMV.

 

[Ritten]

PTG has a 700 action wrench that torques down similar to the Surgeon wrench, but it enters from the rear of the action so it works well with LH actions. I use 100 ft/lbs. but none are designed to be switch barrels.

 

[bward]

100 ft/lbs is a widely accepted torque setting. +/- a few ft/lbs won't hurt anything. I would just try to keep it constant when switching back and forth.

 

[Greg Langelius *]

It is questions like this that make me a believer in the concept of a barrel nut.

Greg

 

[LRI]

Theres 2 principle concepts to observe when asking a question like this and its important to know how to distinguish the two.

1. Group size

2. Group center

The simple comparison is the difference between a gun used in BR comp vs a rifle where you need the first shot to find the x ring.

You can hand snap a barrel and shoot itty bitty groups. Theres however no assurance itll hit the same spot from one day to the next.

When you want tiny groups that hold a consistent zero then one has to increase the tension spplied at the threaded joint. Theres a number of variables that can (can, doesnt mean every time) Iinfluence this.

Threaded feature surface finish. -it affects the torque value. If the finish is bad the torque wrench will pop sooner but it doesnt mean the joint is loaded properly.

Thread tolerance between two mating parts -loose threads tend to distort a bit, again leading to a potentially erroneous indicated torque value


Dry assembled or lubricated. -Dry threads lock up sooner due to friction on the thread flanks and the shoulder. Again the joint may not be preloaded.

Type of lubrication used -baby oil. Not so much. You need a lube with a high shear load tolerance.

Caliber. Big boomers make more drama than little stuff.

Bullet weight. ^whut he said

Barrel length. More leverage out on the end

Twist rate. Mix with big bullets and aggressive ROT and you need a solid thread union.

All of these have shown to influence the final outcome. Theres no single answer other than to put the bugger on RFT if you want repeatable results. Just cause Bobby does a light torque on his 223 doesnt mean your 338LM is going to behave the same way.

Hope this helps.

C.