Barrel Torque Ludicrocity

#201
bohem said:
The print we have says 0.825 +/-1, where is the 822 number published? The 825 number has been standard since 2018 timeframe with the Nucleus launch and several shops, myself included, argued with Ted to make the 825 number standard and keep it for the Coups. We've never run into an issue with the Coup on headspace using 825.

Or does someone else have an old print or an incorrect reference entirely? Instead, using 825 all the numbers match up there.

I did see some early Nukes that were 822/823 range and that caused some very early, very rare issues being that we were cutting the barrels at the time to 823+/- 5 tenths since the number ARC gave me was 825 +/-1, however I haven't seen anything like that since 2018 Gen 1 Nukes.
Click to expand...

Document control is always fun!

Don't even get me started on document control and revision control... Was just dealing with that last week actually, the customer emailed one of the program team that was on vacation a redline that didn't make it to document control, and now I have 5 parts in inspection that weren't made to the current rev that need rework, lol

Always fun when you have drawings that are into the double digits of revisions (better yet, double letter revisions which means at least 26 drawing revisions) and you need to keep manufacturing, inspection, vendors, and the customer all working to the current rev... Especially if while you're making parts to the current rev you also need to make spares for decades old aircraft that may require you dig out an old rev and make a specific down rev version of the part for that specific aircraft. So many opportunities to screw up!
 
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#202
Kiba said:
Document control is always fun!

Don't even get me started on document control and revision control... Was just dealing with that last week actually, the customer emailed one of the program team that was on vacation a redline that didn't make it to document control, and now I have 5 parts in inspection that weren't made to the current rev that need rework, lol

Always fun when you have drawings that are into the double digits of revisions (better yet, double letter revisions which means at least 26 drawing revisions) and you need to keep manufacturing, inspection, vendors, and the customer all working to the current rev... Especially if while you're making parts to the current rev you also need to make spares for decades old aircraft that may require you dig out an old rev and make a specific down rev version of the part for that specific aircraft. So many opportunities to screw up!
Click to expand...
Yeah, no shit. That part sucks
 
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#203
bohem said:
The print we have says 0.825 +/-1, where is the 822 number published? The 825 number has been standard since 2018 timeframe with the Nucleus launch and several shops, myself included, argued with Ted to make the 825 number standard and keep it for the Coups. We've never run into an issue with the Coup on headspace using 825.

Or does someone else have an old print or an incorrect reference entirely? Instead, using 825 all the numbers match up there.

I did see some early Nukes that were 822/823 range and that caused some very early, very rare issues being that we were cutting the barrels at the time to 823+/- 5 tenths since the number ARC gave me was 825 +/-1, however I haven't seen anything like that since 2018 Gen 1 Nukes.
Click to expand...

I googled "ARC tennon Specs" and the first relative link that popped up showed the below image. If you go to their website, Support page links to the same CDG pdf with 0.822. One link below is their other actions which says "not for CDG" and indicates a 0.825".
1760719397677.png


1760719507735.png
 
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#205
The ramp thread from Harolds book is money. Absolutely solves the problem, EXCEPT that you will yield the action face, recoil lug or barrel shoulder. Back to square one.

Accept that it will not be tight enough to stay together (magnum diameter case @65k plus) and the right way is to make the thread and shoulder interface as perfect as we can so it can return to the same place. Advantage integral lug, advantage integral base (or no penetrating scope mounting screw), advantage high speed CNC threading, advantage perfectly orthogonal face/thread.

Lighter psi and smaller diameter case do not exp the separation issue.

FYI AR style joints are different, require a different discussion.

Takeaway is: not too tight is the right answer. Too tight should at least be determined by calculation, and stay a safety factor below. 75-100 is just right as a general spec. The friction coefficient is a HUGE player in this problem/solution also.

Barrel joint movement due to everything but recoil is the boogey man that destroys my peaceful nights!
 
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#206
I don’t claim to know anything about nothing, but what role does the recoil lug play when torquing an action on to a barrel?

•What material is the lug made from?
•What is the quality of a given material?
•Overall machining quality and consistency?
•Is the material heat treated?

…Just to rattle off a couple of questions that come to mind.

I spoke on the phone with a well known Jedi Master that has used recoil lugs that were apparently made from the same material and process as a Spuhr clamp bar, which raised the question about barrel torque.
 
#208
I talked with Mike R today and asked about the amount of force he uses in his rifles because I had one of his rifles and it never shifted poi cold or hot action, unlike many other bolt actions have

He explained he uses way more torque than most and has his barrel lugs made of special steel that is 45 Rockwell hardened so it does not smash from the torque to accomplish the task. Well he went into far greater detail than that but it was over my head. All I can say is what Tac Ops does works

So I don’t know the minimum torque required but I know it’s a lot more than some here are using
 
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#209
wind gypsy said:
I googled "ARC tennon Specs" and the first relative link that popped up showed the below image. If you go to their website, Support page links to the same CDG pdf with 0.822. One link below is their other actions which says "not for CDG" and indicates a 0.825".
View attachment 8788934

View attachment 8788935
Click to expand...
This is the EXACT print......and the one linked to their website.

I understand things change, so I always check the manufacturer's website to make sure I get the updated specs.

Don't get me wrong, I am not shitting on ARC.......I just made a decision to no longer offer prefits based on their own print/action inconsistency.

It sounds like .825 +/-.001" is pretty consistent from Bohem and others. However if I am cutting to a print.......then I am cutting to a print......and the burden of error/design is not mine. This is basic machining 101.

I also believe in providing the best customer service and experience possible. Given all this information, the best solution for me moving forward is to have any ARC action in hand when fitting a barrel.

Ern
 
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#211
MikeMiller said:
I talked with Mike R today and asked about the amount of force he uses in his rifles because I had one of his rifles and it never shifted poi cold or hot action, unlike many other bolt actions have

He explained he uses way more torque than most and has his barrel lugs made of special steel that is 45 Rockwell hardened so it does not smash from the torque to accomplish the task. Well he went into far greater detail than that but it was over my head. All I can say is what Tac Ops does works

So I don’t know the minimum torque required but I know it’s a lot more than some here are using
Click to expand...
Talking to Mike is dangerous… Surprised he didn’t sweet talk you into buying another TacOps before y’all hung up. lol
 
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#212
Aaron Davidson said:
I believe that the thread operates the same as a std rem style. Only one side of the thread is in contact and the opposing force is carried on the barrel shoulder. This diagram would be incorrect.
Click to expand...
Only one side of the thread is in contact, EXCEPT under the “locking tab”, or wtfe you want to call it. When the pinch screw is tightened, the tab is pushed until the lead and flank of the tenon thread are are making contact with the lead and flank of threaded locking tab.

I’ll admit, since the tab is already in contact with the flanks while hand tight, the locking tab being forced slightly further down the flank (maybe .002-.003”?) will very slightly increase tension on the tenon, but it will be minimal spring tension from the tab flexing, before it almost immediately also contacts the lead side of the threads, creating a clamping force (loading both the lead and flank)

The redlined loading in diagram is correct under the locking tab of the AXMC.
 
#213
I torque them to 100+. After 110-130 the nut stops moving and the torque just starts ramping so I figure it's done.
I use a bending bar style torque wrenches so I can see the torque, no clickers for me.

Copper based high heat anti-seize because that's what's been on my bench for years.

The M14 (9/16"ish) studs on my truck call for 160 ft lbs. Pretty sure a 1"+ thread isn't going to get hurt by 100-200 ft lbs. (Obviously if you're not using steel this all goes out the window).
 
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#215
Ronin22 said:
Tell machinists this and they’d horse laugh you out of the fucken galaxy.
Click to expand...
Engineer here. I tell machinists what to do all the time, and they don't horse laugh me out of the galaxy. In fact, their work doesn't go anywhere, until I sign it off, because I bear the liability. I'll be the first to tell you that 100 foot pounds of torque on a rifle barrel is diddly squat. The average rifle barrel threads have about 100 KSI tensile strength. As a point of reference, assuming that this was a fastener, and that you don't lubricate the threads, you would expect operating torque to be somewhere around 1200 ft-lbs, on the high end. Assuming that you lubricate the threads, it's still somewhere around 950 ft-lbs.

There's nothing really controversial about 100 foot pounds. No, it's not a drop in prefit, at that point. But it's still well below what a standard torque engagement would be for a fastening application. And if it shoots better, why argue? I had a gunsmith talk me into it on one of my Zeus actions, and I've never looked back since.
 
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#216
Mike Casselton said:
After writing the above, my mind drifted back to the wing attach bolts on an F-16.
The 12pt nuts weren't all that big in diameter, and they were close to 2000lb/ft on the bolt side.

I'm just gonna say the action could possibly handle that big of a torque.
Click to expand...
The highest tensile strength super alloys come in at about 250-300 KSI. At that strength, a fastener would be around 1 inch in diameter to be able to withstand 2,000 ft-lbs of torque.
 
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#220
Rubicon Precision said:
Only one side of the thread is in contact, EXCEPT under the “locking tab”, or wtfe you want to call it. When the pinch screw is tightened, the tab is pushed until the lead and flank of the tenon thread are are making contact with the lead and flank of threaded locking tab.

I’ll admit, since the tab is already in contact with the flanks while hand tight, the locking tab being forced slightly further down the flank (maybe .002-.003”?) will very slightly increase tension on the tenon, but it will be minimal spring tension from the tab flexing, before it almost immediately also contacts the lead side of the threads, creating a clamping force (loading both the lead and flank)

The redlined loading in diagram is correct under the locking tab of the AXMC.
Click to expand...
No.
 
#221
Ronin22 said:
lol.
Really though. 100ftlbs for prefit barrel torque? Fuck, I know this isn’t necessary. AR15 armorer schools is min 35ftlbs unless old school barrel nut needs advanced to next cut out for gas tube clearance. Then it’s 35-65ftlbs range.

I run 55ftlbs on my bolt gun Savage style barrel nut torque. Easy on off with anti-seize. 300WM too.

Seems excessive in regards to thread distortion and will a 35ftlbs barrel ever shoot loose? No human can spin loose a 30ftlbs barrel.
Click to expand...

Somebody may have answered this in the 4 pages I didn't read but they didn't on the first so I'll provide my understanding of the reason.

The reason for very high 100-150 ft lbs of torque on a barrel is not related to the barrel coming loose. It is related to the amount of elastic deformation you will get in the threads during the shot. Because the bolt lugs are in the receiver on the types of bolt gun we are talking about, the immense pressure from a shot will be applied to the threads between the barrel and the receiver. If not substantially pre-loaded by a high barrel torque these threads will stretch a lot further than if they are pre-loaded. This stretch makes the chamber temporarily longer during the shot resulting in over-expansion of the brass and a likelihood of stuck cases. I'm sure it's also not ideal for your accuracy but I doubt that is really as big of an issue. And yes, I did notice that Ted became very obsessed with the problem of stuck cases right around the time of the barloc system.

As for barrels with extensions containing the lugs such as on an AR or on some euro-ish bolt actions, they don't require high torque on the barrel nut because those are not the threads that will be loaded by the chamber pressure. The chamber pressure loaded threads are between the barrel and the barrel extension in that type of system. As such, it is much easier to make a switch barrel system if your using a barrel+extension system than one with the locking lugs in the action.
 
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#222
BigJimFish said:
Somebody may have answered this in the 4 pages I didn't read but they didn't on the first so I'll provide my understanding of the reason.

The reason for very high 100-150 ft lbs of torque on a barrel is not related to the barrel coming loose. It is related to the amount of elastic deformation you will get in the threads during the shot. Because the bolt lugs are in the receiver on the types of bolt gun we are talking about, the immense pressure from a shot will be applied to the threads between the barrel and the receiver. If not substantially pre-loaded by a high barrel torque these threads will stretch a lot further than if they are pre-loaded. This stretch makes the chamber temporarily longer during the shot resulting in over-expansion of the brass and a likelihood of stuck cases. I'm sure it's also not ideal for your accuracy but I doubt that is really as big of an issue. And yes, I did notice that Ted became very obsessed with the problem of stuck cases right around the time of the barloc system.

As for barrels with extensions containing the lugs such as on an AR or on some euro-ish bolt actions, they don't require high torque on the barrel nut because those are not the threads that will be loaded by the chamber pressure. The chamber pressure loaded threads are between the barrel and the barrel extension in that type of system. As such, it is much easier to make a switch barrel system if your using a barrel+extension system than one with the locking lugs in the action.
Click to expand...
I like it! So, what is going on with a Savage barrel nut rig? The threads are also inside with the bolt head. Then there is the nut. So is that mechanically locked vs tension of threads?
 
#228
BigJimFish said:
The reason for very high 100-150 ft lbs of torque on a barrel is not related to the barrel coming loose. It is related to the amount of elastic deformation you will get in the threads during the shot.
Click to expand...
Maybe this explains what I've experienced since I switched back to my 6.5CM barrel last week, preparing for a match at a venue known for longer ranges and a fair amount of wind.

I only torqued the barrel to 50 ft/lb, less than the 75ish used in the past. Using my well-established load - Berger 140 HT at 2750ish from 7x-loaded Peterson brass fired only in that barrel - all of a sudden I'm getting a little "click" at the top of the (Defiance Deviant) bolt lift in maybe half the rounds. Haven't had that before. Brass looks fine; no primer flattening or ejector swipe.

Accuracy... meh. Half-inch @100, but should be a little better.

I'm gonna put on another 30-50 ft/lb and see what happens.
 
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#229
lash said:
Fair question. I wouldn’t know for sure, since I have both a Savage .338 that shoots one hole groups and a .260 Remage that does the same.
Click to expand...
Yeah, so long as the barrel shoulder or nut faces are trued square and mated with a squared action face, I am at a loss to know the differences.
Could it all be a huge bias against the aesthetics of a nut job? LOL
 
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#230
Tokay444 said:
No.
Click to expand...
What part? You don’t think the locking tab flexes enough to make contact with the lead and flanks of the thread under it?

Do you think AXMC locking mechanism holds the barrel from coming loose due to the increase in tension in the threads or simple clamping? Do you think the increase in tension from the locking mechanism would be equivalent to the barrel being torqued to 50lbs? 100lbs+?
 
#232
Lightning8 said:
At what torque will the home hobbyist have issues removing a prefit barrel? I run prefits in Impact actions, at some point the value of a prefit is lost if I have to take the barreled action to a gunsmith to remove the barrel.
Click to expand...
This is something I have considered as well. I can get off 55-80 ok on my set up. Last one I removed at 100ftlbs I had to remount the lag screw through my bench. Yes, the answer is a more stable set-up, but it's really convenient to take off a barrel or a nut without a lot of drama.
 
#234
Rubicon Precision said:
What part? You don’t think the locking tab flexes enough to make contact with the lead and flanks of the thread under it?

Do you think AXMC locking mechanism holds the barrel from coming loose due to the increase in tension in the threads or simple clamping? Do you think the increase in tension from the locking mechanism would be equivalent to the barrel being torqued to 50lbs? 100lbs+?
Click to expand...
If you put a strain gauge between the shoulder of the barrel and the receiver, you’ll observe force climb exponentially as you tighten the crosse screw.
Well above 100ft/lbs, and it’s not what I “think” or “feel”.
 
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#235
BigJimFish said:
The reason for very high 100-150 ft lbs of torque on a barrel is not related to the barrel coming loose. It is related to the amount of elastic deformation you will get in the threads during the shot. Because the bolt lugs are in the receiver on the types of bolt gun we are talking about, the immense pressure from a shot will be applied to the threads between the barrel and the receiver. If not substantially pre-loaded by a high barrel torque these threads will stretch a lot further than if they are pre-loaded.
Click to expand...
This actually is not correct. To be clear, for a rifle barrel, this is not high torque, at all. It is somewhere around 10% of the yield strength, for many high power rifles.

Elastic deformation is a measure of how much force can be applied to a material, without permanently altering its physical properties. When we over tighten a fastener, we have exceeded its elastic limit. If we have not achieved ANY elastic deformation, we have not applied any clamping force.

Torque values are all about clamping force, pure and simple. We have to achieve enough to keep our threads engaged. Sometimes we want maximum clamping force and other times we don't. In the case of a rifle, where we have Dynamic conditions that produce multiple simultaneous forces, there needs to be a minimum value. But once we have achieved the minimum to overcome things like thread back out, induced by Barrel vibration, then we have to start taking a more analytical approach about the gains that are made by the values we specify. That's not done in the theoretical world. That is the stuff of Laboratories and or lots and lots of instrumented testing.
 
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#238
This thread is proof why I let very few people touch or cut my barrels. The absolutely stupidity coming from people is all the proof you need.

Over the last few years I have slowly lowered torque on actions from 70 to 60 to 50 to about 40 or so. They shoot the same. Less stress on the lugs from internal action wrench. Don't need to squeeze life out of barrel in vise to get off or on. Anything more than 30-40lbs is pointless.
 
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#241
DeathBeforeDismount said:
This thread is proof why I let very few people touch or cut my barrels. The absolutely stupidity coming from people is all the proof you need.

Over the last few years I have slowly lowered torque on actions from 70 to 60 to 50 to about 40 or so. They shoot the same. Less stress on the lugs from internal action wrench. Don't need to squeeze life out of barrel in vise to get off or on. Anything more than 30-40lbs is pointless.
Click to expand...
This thread has an interesting data set from 40-800ftlbs. 🤣
 
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#243
DeathBeforeDismount said:
No kidding. Retards comparing lug nuts on a 5k+ LB vehicle to a precision rifle takes the cake. I would love to know what kind of fixture people use to install and break free 100lbs+. I can damn near rip a 400lb bench bolted and epoxied off the wall taking a Tikka barrel off.
Click to expand...
But have you thrown your 40# torqued rig off a two story building onto concrete and had a POI shift? 🤣

Ironic, I actually started this thread after pulling the 5” lag screw out the bench of the barrel vise breaking free 100ftlbs barrel.
 
#248
AccuSol-ERN said:
I would love to get the action makers response to some of the large torque numbers suggested.

Ern
Click to expand...

They won't suggest torque that high as I'm sure they want to avoid their phones blowing up with people asking to return/exchange their damaged or marred up actions and barrels after trying to get things that tight with the incorrect tooling for the job, lol


Just some quick math here since I have a few free minutes and I'm bored...

Typical barrel material is 416 stainless, so assume fully annealed condition for the lowest possible yield strength, that's 40ksi.

Let's go with 1.0625" diameter tenon threads.

Target 75% of the 40ksi yield strength for the tensile load on the threaded joint so you're still safely in the zone of good preload but only elastically deforming the threads and not yielding the material, that works out to 26600lbs desired tensile load with a 1.0625" fastener/tenon diameter.

Using a K factor of 0.12 for lubricated fine pitch threads, 1.0625 major diameter, and a target tensile load of 75% of the 40ksi yield strength with a 1.0625 diameter fastener for a desired 26600lb of preload, plug it into T = KDF and that is suggesting a 275 ft/lb torque to achieve 75% of 40ksi yield strength of annealed 416 stainless with 1-1/16" diameter lubricated fine threads.

The math doesn't care what the use case is for the threads, it only cares about the desired preload and material, frictional, and dimensional properties of the threaded joint. (Keep in mind the specific use case may allow a lower amount of preload, or require a higher amount of preload... that's a different subject.)

Again, 100-150 ft-lb is rather low in regards to torque for threads the size of a typical barrel tenon even assuming a fully annealed 416 stainless barrel with threads slathered in anti-seize. At 100-150 ft/lbs things are still well under the yield strength of annealed 416 stainless and you not going to hurt the action or barrel going that tight, and if anything, it might not be enough preload in the joint for maximum cold bore / zero stability in all use conditions.

As far as what is appropriate torque as far as what you consider to be "tight enough" for repeatable accuracy and what your workholding and fixturing is capable of handling without slipping/gouging/marring/breaking anything, that's up to you. I shoot for 125 ft-lb on my own stuff as much tighter than that the barrels can be a pain in the ass to pop free after being installed for a while; I'd rather not mar up the external surfaces or twist or damage the action/raceways/lugs with an internal action wrench. 125 ft-lb is what I consider the "reasonable" number for my tooling and fixturing, but if I had tooling that would handle 200-300 ft-lb without any worries about marring or damaging the action or barrel that's the range I would be more satisfied using based on the thread diameter and material properties involved.

Better yet would be to use the lowest torque that the data says is needed to minimize or eliminate cold bore POI deviation and POI deviation after a significant impact event on the barrel, but I do not have adequate test data to make that determination.

Disclaimer: I did the above calcs quickly on my phone and may have messed up, so keep that in mind, lol. However, for a rough sanity check of my math, looking up suggested torque charts for an M27 fine thread bolt (M27 = 1.063", so very close to my example) in grade 4.6 (4.6 = 400 MPA tensile strength, 0.6 * 400 = 240 MPA yield strength, and 240 MPA = 34.8ksi yield strength, so weaker but somewhat close to the 40ksi of annealed 416 stainless I used) shows a suggested lubricated torque value of 360 Nm / 250 ft-lbs on several bolt manufacturers data charts.
 
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#249
To you machinists/engineers.. What is the difference between a torque spec for a standard 5/8-11 fastener and one for a Cat 40 retention knob / pull stud? What happenes when you exceed the retention knob torque value?
 
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