Does this gunsmith know something that the rest of us do not?

I'm just making a statement from my reading and not from personal experience. I understand that when torqueing a centerfire barrel the extra torque added beyond barrel shoulder and action contact causes a distortion of the chamber underneath from the pressure upon the shoulder. In a centerfire this doesn't cause a lot of problems since it is a radial load upon the chamber portion of the barrel and unless it causes a problem with extraction doesn't affect a lot. On a rimfire however, that same torque causes a distortion upon the rifled portion of the barrel just forward of the chamber. This tight spot can destroy accuracy in a rimfire by constricting the bore at that point to a diameter smaller that the rest of the barrel. It makes sense. I've been reading the Calfee articles in some old PS backissues I bought hoping to learn something. What's the thinking?
 
Whelenman,
I think you're right. JGee is asking rimfire questions and getting CF answers. They're two different animals.
 
WhelenMan said:
I'm just making a statement from my reading and not from personal experience. I understand that when torqueing a centerfire barrel the extra torque added beyond barrel shoulder and action contact causes a distortion of the chamber underneath from the pressure upon the shoulder. In a centerfire this doesn't cause a lot of problems since it is a radial load upon the chamber portion of the barrel and unless it causes a problem with extraction doesn't affect a lot. On a rimfire however, that same torque causes a distortion upon the rifled portion of the barrel just forward of the chamber. This tight spot can destroy accuracy in a rimfire by constricting the bore at that point to a diameter smaller that the rest of the barrel. It makes sense. I've been reading the Calfee articles in some old PS backissues I bought hoping to learn something. What's the thinking?
Click to expand...

Thanks Mr. Whelenman!! I guess that's why i asked, i wasn't even thinking in that direction but you would be strecthing/pinching/something in the chamber right at the rifleing on a rimfire.

That damn Calfee thinks of evrything -maybe i could learn to like him, lol!! joe :)
 
What might work on a rimfire may well get someone hurt with a centerfire. Factory rimfires have barrels pressed in, pinned in, clamped in (Ruger), and probably others too. The first three would likely end up with the barrel and action in two separate pieces. There's also a lot of difference between hand tight and 100 ft lb. Most car lug nuts are spec'd to be torqued to around 90 ft lb of more. That's easily done or overdone with a star lug wrench. Not excessively tight IMHO. I'm not sure how much torque will cause accuracy to decrease, but loose definitely will.
 
Larry,
I agree that a CF barrel should be tight and the RF barrel should be tight enough to stay put, but not so tight to distort the chamber and or bore.
Like I said, two different animals, and using the same rules for both could be a dangerous proposition.
 
JerrySharrett said:
Al, headspace is not going to change by loading the threaded joint until you reach the yield point of the barrel material and that is probably beyond 120,000 # load.

A basic explanation of yield can be seen at
http://en.wikipedia.org/wiki/Yield_(engineering)
Click to expand...

Jerry, I know that. :)

The idea has been bandied about a bit on this forum of late.... And I like the way Greg thinks and tests stuff and passes it on.

I understand that the headspace is set by the junction of the shoulder to the action face and that even if you DID actually stretch the threads it would only decrease the gap between the barrel and bolt lug face.

It's just that when someone like Walley or Borden or Scott says it, it carries some weight.

Silly of me, and a JOKE...... prolly shoulda' just shut up!

(but you know me.....)

LOL

al
 
Gentlemen,
What about the action threads ? Do they stretch or become fatigued by years of reefing tight barrels on and off ? Does one increase the odds of galling threads or shoulders when he really leans on the action wrench.
I have stripped too many threads and twisted too many heads off of bolts throughout the years.I don't want to do that to my $1000 action.
Joel
 
Nader said:
Gentlemen,
What about the action threads ? Do they stretch or become fatigued by years of reefing tight barrels on and off ? Does one increase the odds of galling threads or shoulders when he really leans on the action wrench.
I have stripped too many threads and twisted too many heads off of bolts throughout the years.I don't want to do that to my $1000 action.
Joel
Click to expand...
Joel, the thread faces will actually become work hardened on the surface making them more durable. A couple of hundred foot pounds are not going to fatigue them.

I've taken Remington 700's apart that required over 500 ft/lb to break the joint. (A 500 ft/lb impact wrench would not break the joint and we had to go to a 900 ft/lb monster). Granted Remington puts some glue-crap on them to really make things difficult but when twisting a 700 action body takes place and the joint is still intact, I don't worry about a couple of hundred foot pounds doing damage.

But don't let all this lull you into not cleaning the threads and applying a good EP grease before assembly, especially on these Stainless to Stainless threads.
 
Barrel tightness

Although I have never relied on hand tightened barrels, I find that torque figures are a little deceptive. The lube has a great affect on the amount of torque needed. Jackie has used a system that works well for me. After snapping the barrel tight by hand, he moves the barrel about 1/8th of an inch farther with the wrench.

Once I was changing barrels at the Super Shoot and Dwight Scott walked by. I asked if I was tightening my barrel enough. He observed and told me that he liked a little more. Although this was a subjective measurement, I gave it an extra bit of torque. If Dwight likes approximately 100 pounds, that is good enough for me. Good shooting....James
 
Joel

Actually, 100 to 150 ft pounds of torque on a 1.062 thread is not very much. In fact, most fasteners of that size in industrial use that are required to firmly secure two pieces use a torque figure that is bordering on four digits, depending on the amount of "stretch" that the manufacturer recommends.

I have one action that has probably had well over 30 barrels on it. It is a Farley on my favorite Sporter, which I bought in 1997. As best I can tell, the threads are exactly as they were the day I screwd the first barrel on to it. And I do put them on rather tight.......jackie
 
jackie schmidt said:
Actually, 100 to 150 ft pounds of torque on a 1.062 thread is not very much. In fact, most fasteners of that size in industrial use that are required to firmly secure two pieces use a torque figure that is bordering on four digits, depending on the amount of "stretch" that the manufacturer recommends.

I have one action that has probably had well over 30 barrels on it. It is a Farley on my favorite Sporter, which I bought in 1997. As best I can tell, the threads are exactly as they were the day I screwd the first barrel on to it. And I do put them on rather tight.......jackie
Click to expand...

In my view by the very nature of the action "thickness" at the threads... sometimes industrial standards my not exactly cross over to gun torque. the lug nut example that has been used in this thread, the torque value for a 1/2" wheel stud is 90 ft pounds of torque -look at the thickness of the lug nut, your probably already thicker than an action at the bbl threads.

There are probably no absolutes for anything, there are always exceptions. Take the case of a 1" industrial bolt. The nut or threads you will torque the 1" bolt into more likely than not will be as thick or thicker than the entire action with the bbl threads removed! Think about the size of a nut for the 1" bolt and compare that nut to the thickness of the action- the action is probably 1/10 the thickness.

When talking torque values around 100 ft pounds, to me the action threads are starting to fall way behind industrial values. I now know 100 foot pounds seems to be the excepted norm... maybe not for rimfire but centerfire does seem to have accepted the 100 ft pd value. joe:)
 
Ok

How about just plain old anecdotal evidence.

Thousands of Benchrest Shooters, who go through more barrels than just about anybody, have been tightening barrels at 100+ ft pounds for years, with absolutly no ill affects.

I actually tighten mine tomore like 130.

How do I know this. I welded a hex on the back of my action wrench so I could use a socket and a torque wrench. I tighten my barrels like this. I snap it up so it is seated firmly. I then take a Sharpie pen and scribe a line connecting the action reciever ring and the barrel. I then tighten the barrel untill there is 3/32 inch movement between the two lines.

With a 1.062 16 tpi, it takes about 130 ft pounds to accomplish this.

I sure hope that the following men read this post and decide that just "snapping it" up is tight enough......Gene Bukys, Gary Walters, Vic Smith, Charles Huckeba, Cecil Tucker, Mike Conry, Leon Glass, Jay Lynn Gore (and his "little fat buddy:D), Larry Bagget, Butch Lambert, Joe Kubon, Dr. Tim, Dickey P, Scott Hunter, John Horn, Richard Futch, Nick Marino, Bob Estes, John Jones, Don Geraci, Joe Bogard David Williams, and a host of others.

This will make life MUCH easier for me in The Gulf Coast Region........jackie
 
This one I agree

Like I said before, I tighten may barrel the same way every time. After it's snapped to the reciever, I tighten 1/8" more. I've never had a barrel loosen when I done them like that. Most RF actions, will not accept a tool that you can turn with a torque wrench. Mine are either Winchester 52's, Hall or Suhls.

CF vs RF equates to Apples and Oranges.

WhelenMan said:
I'm just making a statement from my reading and not from personal experience. I understand that when torqueing a centerfire barrel the extra torque added beyond barrel shoulder and action contact causes a distortion of the chamber underneath from the pressure upon the shoulder. In a centerfire this doesn't cause a lot of problems since it is a radial load upon the chamber portion of the barrel and unless it causes a problem with extraction doesn't affect a lot. On a rimfire however, that same torque causes a distortion upon the rifled portion of the barrel just forward of the chamber. This tight spot can destroy accuracy in a rimfire by constricting the bore at that point to a diameter smaller that the rest of the barrel. It makes sense. I've been reading the Calfee articles in some old PS backissues I bought hoping to learn something. What's the thinking?
Click to expand...
 
jGEE said:
In my view by the very nature of the action "thickness" at the threads... sometimes industrial standards my not exactly cross over to gun torque. the lug nut example that has been used in this thread, the torque value for a 1/2" wheel stud is 90 ft pounds of torque -look at the thickness of the lug nut, your probably already thicker than an action at the bbl threads.

There are probably no absolutes for anything, there are always exceptions. Take the case of a 1" industrial bolt. The nut or threads you will torque the 1" bolt into more likely than not will be as thick or thicker than the entire action with the bbl threads removed! Think about the size of a nut for the 1" bolt and compare that nut to the thickness of the action- the action is probably 1/10 the thickness.

When talking torque values around 100 ft pounds, to me the action threads are starting to fall way behind industrial values. I now know 100 foot pounds seems to be the excepted norm... maybe not for rimfire but centerfire does seem to have accepted the 100 ft pd value. joe:)
Click to expand...

Not really Joe.

The thickness of the action or the nut is irrelevant, within reason..............its the thread strength itself.............in the case referenced by Jerry, a 1"-12 TPI Class 7 thread is the same whether its machined into an action cylinder or a large industrial nut cylinder, they both can be torqued to 700 ft lbs or more............Don
 
jackie schmidt said:
How about just plain old anecdotal evidence.

Thousands of Benchrest Shooters, who go through more barrels than just about anybody, have been tightening barrels at 100+ ft pounds for years, with absolutly no ill affects.

I actually tighten mine tomore like 130.

How do I know this. I welded a hex on the back of my action wrench so I could use a socket and a torque wrench. I tighten my barrels like this. I snap it up so it is seated firmly. I then take a Sharpie pen and scribe a line connecting the action reciever ring and the barrel. I then tighten the barrel untill there is 3/32 inch movement between the two lines.

With a 1.062 16 tpi, it takes about 130 ft pounds to accomplish this.

I sure hope that the following men read this post and decide that just "snapping it" up is tight enough......Gene Bukys, Gary Walters, Vic Smith, Charles Huckeba, Cecil Tucker, Mike Conry, Leon Glass, Jay Lynn Gore (and his "little fat buddy:D), Larry Bagget, Butch Lambert, Joe Kubon, Dr. Tim, Dickey P, Scott Hunter, John Horn, Richard Futch, Nick Marino, Bob Estes, John Jones, Don Geraci, Joe Bogard David Williams, and a host of others.

This will make life MUCH easier for me in The Gulf Coast Region........jackie
Click to expand...

Ouch!! "snapping it" can have 2 meanings, lol. :D:D:D Jackie don't i have some kind of point???

I'm 60 years old, i'll be real lucky to hit 70... there is no way i will ever know what you guys know Mr. jackie you done forgot more than i got years left to learn.

Do you guys "over torque" just because you don't know how to weld :D:D:D:D .. hey just kiddin, it's all good. I'm about ready to throw my junk in a dumpster anyway. joe :)
 
Okay... coming from the 'just a bit past snug' camp myself... how much difference in accuracy have you guys seen between 'hand tight' and 'wrenched down'? Are we talking difference between nearly zero groups and say, 'just' sub 0.2, or between sub 0.2 and 0.4-0.5... any difference on long range guns i.e. do they wrench the barrels down tight as well, or not?

Thanks,

Monte
 
Don said:
Not really Joe.

The thickness of the action or the nut is irrelevant, within reason..............its the thread strength itself.............in the case referenced by Jerry, a 1"-12 TPI Class 7 thread is the same whether its machined into an action cylinder or a large industrial nut cylinder, they both can be torqued to 700 ft lbs or more............Don
Click to expand...

The strength of the joint is determined by the weaker of:
  1. the thread itself,
  2. the cross sectional area of the metal outside the female threads, and
  3. the effective stress cross section area of the metal inside the male thread.

If the length of thread is too short the thread strength may be the limiting factor. If the effective stress area of the metal in the receiver body is small enough that the stress exceeds rupture, the receiver will fail. The barrel itself is the strongest part of the joint since in most cases it has the most cross sectional area that resists stress.

If one takes a look at any of these factors, in a rifle barrel to receiver joint the stresses from torquing the threaded joint are a rather small fraction of what would be required to deteriorate the receiver material for any practical torque.

On that basis, the torque is irrelevant.

However, if one analyzes a threaded joint, it is the joint preload that is critical to joint performance. The joint preload (established by the tightening torque) needs to be enough to prevent the joint from moving, from experiending internal seperation of mating surfaces during normal expected activities involving the joint, that would include, in this case, the rifle firing.

I can't tell you how much torque that would take, but if the torque isn't enough to provide a preload stress that will stabalize the joint, there is going to be more flex between the barrel and the receiver.

Will this lack of stabilization and flex be detrimental to accuracy? One extreme case is when the barrel is basically just touching and is in fact loose. It is well known that condition can cause significant loss of accuracy. As the barrel gets tighter there should come a point where the flexing goes below the threshold of significance and group sizes won't get any smaller.

I don't have any data that would allow making an estimate of that situation.

So qualitatively, that's the situation. Maybe one of these days Varmint Al will fire up his finite element analysis machine and model this situation. That's about the only way to get a real understanding of it quantatively because the phenomena that determines the installation torque is the result of dynamic behavior.

In the mean time, the instructions with my wheeler wrench suggest 40 ft-lbs for the savage barrel nut, so that's what I torqued it to.

The 100 ft-lbs sounds reasonable for other actions with a shoulder, especially if it's been done a lot and barrels don't come loose, but I have no objective basis for being able to say it's enough or not.

Fitch
 
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