Hand tight switch barrel accuracy?

[25WSM]

If your using one of the portable bench vises that the BR guys use it virtually impossible to put a barrel on too tight to the point of hurting anything. The barrel will slip in the vise before you get that much torque on it. That's why factory torqued barrels can't be removed that way. I personally wouldn't have a clue how to calibrate a torque wrench. Above my pay grade. But would it really matter much if your barrel was 25 pounds or 30 pounds. Or even if it went on tighter to 35 pounds. I doubt you could tell on paper. But it would be nice to have a tool that was correct. Especially if your bolting on wings of the plane I'm flying in.
Shep

 

[ducky]

I've built a lot around the Savage action just to use the barrel nut, any future builds where I barrel swap will probably get a WTO Switch Lug installed.

 

[ntsqd]

Out of Cal on a beam type is the pointer not pointing to zero with no load applied. Bend the pointer until it does point to zero. Ta-Da! Calibrated!*


*Well, Zero'd anyway, up to the mfg to have made the beam itself the right size and made the scale match it correctly.

 

[Jeffrey Van Zandt]

I am having a barrel spun up for me with a wrench flat on the end to tighten. I was thinking of just having them do away with the wrench flat and screw on hand tight. Does this affect accuracy?

it may work loose some have torque it down anti seize the threads and face have done switch barrel set ups and no trouble with the on or off useing bighorn nut or the sholder fits

 

[J E Custom]

If your using one of the portable bench vises that the BR guys use it virtually impossible to put a barrel on too tight to the point of hurting anything. The barrel will slip in the vise before you get that much torque on it. That's why factory torqued barrels can't be removed that way. I personally wouldn't have a clue how to calibrate a torque wrench. Above my pay grade. But would it really matter much if your barrel was 25 pounds or 30 pounds. Or even if it went on tighter to 35 pounds. I doubt you could tell on paper. But it would be nice to have a tool that was correct. Especially if your bolting on wings of the plane I'm flying in.
Shep

It is common to use a torque wrench to tighten barrels and a very accurate way to get consistent performance. Different uses normally call for different torque values. A bench gun that Is not used hard can be as low as 35 ft/lbs. a hunting rifle should be more depending on the quality of the barrel fit and service. The extreme duty rifle should be at minimum 60 ft/lbs to remain constant under all conditions and uses. Some service rifles may have 90+ ft/lbs if they are subject to full automatic fire where there is a lot of heat build up that could cause a shift in parts.

The main reason for using a torque wrench is to be consistent. If you work up a load and then allow the torque to change (Even slightly) it will change the harmonics and possibly the POI .

Even if the tool is a few pounds off, as long as it is consistent, that is what matters. also the main reason that a torque tool is used is to assure that the torque is the same if a gorilla or a much lighter built person tightens the barrel using the tool, The applied torque will be the same. It is no different than torquing scope base and rings. It is recommended that everyone uses a inch pound torque wrench to prevent over torquing or uneven stress on one screw over the other.

I highly recommend using a torque wrench for all threads, to load the part consistently time after time. Especially if you are changing barrels back and forth. you will want the same stress applied to the part for consistent results. Tightening by hand can't give you the consistency, even if indexed because changes in thread fit and lubricants can change the feel and the amount of rotation of the threads. Thread Assembly compounds will help the consistency if used and reduce the needed amount of torque to get the same loading on the threads by an average of 15 %.

J E CUSTOM

 

[ntsqd]

Lubrication of the thread has a HUGE effect on the result. Have a look at this chart: https://www.portlandbolt.com/technical/bolt-torque-chart/ and notice the different torque requirements needed to achieve the same tensile loading in the bolt. That is just the first such chart that I found, there are many like that.

In highly critical assemblies even a torque spec is not good enough. On fasteners like racing connecting rod bolts best practice is to measure how much the fastener stretches as the nut is tightened. Their "torque spec" is related as being ".009 stretch" and similar. Some German engines were the early adopters of torque to some low setting plus an angular measurement of further thread rotation. So a spec for one of those bolts would be "23 ft-lbs + 45°"

I don't see the former being terribly practical in firearms, but the latter method has some merit & may be worth some investigation.

 

[J E Custom]

Lubrication of the thread has a HUGE effect on the result. Have a look at this chart: https://www.portlandbolt.com/technical/bolt-torque-chart/ and notice the different torque requirements needed to achieve the same tensile loading in the bolt. That is just the first such chart that I found, there are many like that.

In highly critical assemblies even a torque spec is not good enough. On fasteners like racing connecting rod bolts best practice is to measure how much the fastener stretches as the nut is tightened. Their "torque spec" is related as being ".009 stretch" and similar. Some German engines were the early adopters of torque to some low setting plus an angular measurement of further thread rotation. So a spec for one of those bolts would be "23 ft-lbs + 45°"

I don't see the former being terribly practical in firearms, but the latter method has some merit & may be worth some investigation.

I ran some torque test using different thread assembly lubes and this is what I found out.

After verifying all surfaces were square and clean on the barrel to action connection, using a quality torque wrench, I torqued a barrel to 70 ft/lbs (The recommended torque for the service) then I scribed a very fine line across the barrel and action on the bottom. After disassembly, I then used ARP assembly lube and to cote the threads and re torqued until the scribed line was perfectly lined up with a magnifying glass and read the torque. On 1 1/16 x 16 threads it read 54 ft/lbs 16 ft/lbs les torque with the same tensile stretch/loading. It also elematited any chance of gaulding or chafing the threads.

It is very consistent and requires approximately the same torque to remove the barrel. I now use it on all of my muzzle brake installations for the same reasons. It will also withstand the highest temperatures reached with a firearm,

I tried the same test with other thread compounds and just liked the Benefits and the consistency of the ARP.

ARP | Official Website | ARP Ultra-Torque

arp-bolts.com

J E CUSTOM

 

[MagnumManiac]

I have never seen a difference in accuracy using ANY torque setting. Either from spinning them on by hand with speed, or using a barrel vise to just nip them up, or putting 100lbs/ft on permanent barrels or 60lbs/ft.
In regards to a switch barrel using a shouldered barrel and exact measurements, when that barrel stops, the headspace is set and no matter how much torque you apply, it is a tenth at best change.
The only time I saw an accuracy issue was when I forgot to spin the action on, got distracted and proceeded to shoot with a loose barrel. Hits were feet away from where they should have been.
You don't want any stretch on barrel/action threads...this is bad juju!
You DO want anti-seize though, I find nickel to be best.

Cheers.

 

[ntsqd]

I'd say that it depends on whether or not the barrel/action stretch is in the elastic or into the plastic deformation zones. Elastic - probably OK even if not desired by some. Plastic - that's a permanent change and not good.

 

[MagnumManiac]

I'd say that it depends on whether or not the barrel/action stretch is in the elastic or into the plastic deformation zones. Elastic - probably OK even if not desired by some. Plastic - that's a permanent change and not good.

I'd say that it is virtually impossible to get anywhere near any stretch with a barrel vise set-up. If you use a proper action vise and a barrel wrench, then it is possible to get stretch on the threads, but again, this is not needed or recommended.
Galling of the mating surfaces is a real possibility and have witnessed this on a Howa action and also a Weatherby Vanguard, both stainless models.

Cheers.

 

[adk hunter]

Finding this discussion and the information provided by some of our top shelf gentleman incredibly interesting!! Better than bourbon. At this hour anyway...

Thank you for sharing your vast knowledge!

 

[J E Custom]

Je he doesn't mention a barrel nut in the original post. I think he is using shouldered barrels and using a wrench to tighten them. I also think the barrel nut systems work great for switch barrels.
Shep

I have never barreled a bolt action rifle and used a wrench fit barrel, so I can't offer much advice for this type of fit, but I would think the procedure would still be the same for a consistent fit up. I feel whatever method you use to make up a barrel, it should be consistent and a torque wrench and a thread assembly Lube is the best and most repeatable method I have found.

J E CUSTOM

 

[ntsqd]

Who doesn't recommend it? It wouldn't be my go-to option, but does any authority in the field or mfg specifically recommend against installing so tight as to induce some elastic stretch?

Galling in SS is the fault of an improper alloy combination and/or the lack of correct lubrication. JE's find in the ARP assembly lube would be one of my first choices. That stuff is the standard in race engine shops all over. Those who don't use it are either clueless/cheap, or are using something really expensive like Krytox.

 

[25WSM]

Head bolts get torqued in the 140 pound range. That's more than double or even triple what a barrel goes on at. Regular anti seize is perfectly adequate for barrels. I watched BR guys put them on for yrs with just a little bolt lube. Not saying head stud lube wouldn't work but it's probably overkill. All my personal rifles go on at 30 pounds and customers hunting rifles go on at 60 and never had a galling problem with any lube. Even on my aluminum action faces.
Shep