I think this is important- barrel with 18tpi tenon, should advance .001 for every 10 degrees or so of rotation. I know at some point you are just stretching things, but if its really close to begin with.... I do the math right there?
BARREL TORQUE
- Thread starter billlarson
- Start date
A bigger and real concern when it comes to accurate torque values is the bend that many action wrenches have in them for stock clearance...and yes, lube is a big factor too.
HTSmith
Silver $$ Contributor
Well I'm wandering off topic but you raised the issue of scope rings. I know from experience that you can get them too tight. An engineer from Sightron straightened me out. Bought myself a torque screwdriver and use the manufacturers specs now. Us farmers change hard but sometimes "just before it wrings off" is not the right answer
Dusty Stevens
Shiner
If youve ever seen how scope rings are made youll know you can get them too tight easily. They machine the hole then use a slitting saw to cut the halfs so if the rings are tightened up where the gap is smaller than the slitting saw its not round any longer
Threads provide a tremendous amount of mechanical advantage, especially when lubricated. I'm a bit incredulous that some folks are torquing to 150 ftlbs. That's an incredible amount of clamping force and seems entirely unnecessary as any imperfections in the shoulder or receiver will be straining the barrel.
Tod Hendricks
Gold $$ Contributor
Usually just finger tight, an then...
From Kelbly's web page....for those of us that use their products.
"Before installing a new barrel, apply EP-2 (NCGI Grade 2) or equivalent bearing grease on the barrel threads and shoulder tenon or receiver face. Do not use metallic based “anti- seize”compounds. Using a Kelbly’s Inc., barrel vise and action wrench, first insert the barrel into thebarrel vise and tighten the nuts on the barrel vise.
Then, using the action wrench, turn the action with a minimum of 100 ft./lbs. of torque. If youdo not own a torque wrench, use a T-handle rear entry action wrench and install the barrel withthe same amount of torque as one would use on a typical lug nut for an automobile wheel.Headspace will be within specification when the barrel is installed tightly to the receiver. No witness mark is necessary. Please note that the caliber stamp may not align on the left side of the action after the barrel is installed in the receiver. If you have any further questions about installing your barrel, please contact us via telephone or e-mail."
"Before installing a new barrel, apply EP-2 (NCGI Grade 2) or equivalent bearing grease on the barrel threads and shoulder tenon or receiver face. Do not use metallic based “anti- seize”compounds. Using a Kelbly’s Inc., barrel vise and action wrench, first insert the barrel into thebarrel vise and tighten the nuts on the barrel vise.
Then, using the action wrench, turn the action with a minimum of 100 ft./lbs. of torque. If youdo not own a torque wrench, use a T-handle rear entry action wrench and install the barrel withthe same amount of torque as one would use on a typical lug nut for an automobile wheel.Headspace will be within specification when the barrel is installed tightly to the receiver. No witness mark is necessary. Please note that the caliber stamp may not align on the left side of the action after the barrel is installed in the receiver. If you have any further questions about installing your barrel, please contact us via telephone or e-mail."
Tod Hendricks
Gold $$ Contributor
Do you ever use SPOT Torque Norm?
HTSmith
Silver $$ Contributor
First I ever heard of using Teflon tape on barrel threads. Is this a regular practice?
joshb
Gold $$ Contributor
FGuffey is the only one that knows about proper headspace!!
I get’em snug, then give em a good oomph. About 50lbs. My oomph ain’t what it used to be.
I suspect it was more about dampening than lubricity. Virtually every joint in a rifle moves at high enough frequencies. The question is, at what point can we out shoot that very tiny movement. I don't..or haven't, advocated for it but a drop of blue loctite..or maybe even purple, would likely have the same or better outcome vs. teflon tape. It may be worth testing, though.
When I did some vibration testing, I took a perfectly good glued and screwed rifle apart. It came out of the bedding very nice, so after cooling, I just put it right back into the stock and torqued the screws back to 65in/lbs(pillared). Interestingly, the barrel vibrated at a different frequency than when glued and it shot best at a different tuner setting. Pretty cool, I thought! It proved to me that every joint that isn't somehow mechanically bonded or welded..moves a little. Just a FWIW.
I use 100 ft lbs with moly lube. Did a quick conservative calculation that firing would not unseat the shoulder with this combination.
I think your numbers are probably correct. But, does it have to unseat to move? Think about a bolt on your car(for example) that you torque down and come back weeks later and it's loose again. I'm convinced that high enough frequencies will move the joint without lateral force. Does it matter? That's the real question. Lots of small groups have been fired with hand tightened barrels.
divingin
Gold $$ Contributor
Uninformed question: Wouldn't the act of launching a bullet down a barrel with a right-hand twist tend to tighten a barrel with every shot? The barrel would initially resist the spinning of the bullet, driving it CCW (from the shooters perspective), which is tightening the barrel to the receiver?
I think that if everything is perfectly concentric and perpendicular the torque does not matter, but and it’s a big but if not it need to be tightened enough to not move, a tight connection compensate for lack of perfection.
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