Neck tension Bug

[AWLEAPHART]

Over the years I have played around with the neck tension thing. Always wondering why neck bushings didn't come in .0005 incriments? Also read a lot of articles on this site about neck tension also.
I have the pin gauges.
I have neck turners.
Expanded necks.
k&m force gauge.
I have played around with 22 cal 6mm 6.5 ,257 and 284 with different brands of brass.
Now with all that said-I have been wondering about some type of lube. Thats one thing I have not used. Lube the neck before seating. Also what kinda of lube. All in a nut shell-just chasing that same neck tension at all times. I can do really well with light tension (.0005) with the bullet about to fall out of the case and rifle shoots great but I'm looking for the same constantly with a little more tension.
Thanks Anthony

 

[MagnumManiac]

All of my comp rifles run from .0015"-.0035" tension, and they all get powdered graphite brushed in the necks before charging and bullet seating. I also seat long, and seat to spec just prior to the match.
The lube seems to keep ignition consistent, start pressures over the pressure trace are very uniform, without the lube, some cases have shown significantly higher start pressure, whether this is due to annealing differences or not, case alloy or other factors, I do not know.
Have tried Imperial Dry Neck Lube, I thinks it's Mica based, it was not as good as graphite in my experience. Some prefer to keep the carbon in the neck as it does a similar job.
I also run fairly long jumps, and believe this is why I get better results with the lube, the bullets are released early in the burn, not by friction, but by neck expansion.

Cheers.

 

[ireload2]

Why don't you learn to shoot with near zero grip" You cannot mess up very much with a value near zero.
Have just enough force to hold the bullet in position say 4 oz to 6 oz.

 

[Mozella]

I hate handling individual cases more than necessary. So I lube my bullets by Moly coating them using the wet process. They are very smooth, shiny, and the Moly doesn't come off on my hands or anything else. The process is easy. I use a cheap Harbor Freight tumbler and a dedicated Walmart applesauce jar. I add 300 .223 bullets, a dab of Moly, and water to cover. Two hours later they're ready. I polish them by shaking the whole batch in a big metal baking pan lined with paper towels and drive the moisture out of the hollow tips using a heat gun while shaking the pan.

I run about .002 "seating" force. I doubt if the Moly does much of anything for my bore, but it certainly makes seating my bullets nice and smooth. Precision and SD improve when I use Moly bullets.

I clean my bore after every range session and I don't spend any more time than I used to. The Moly makes the patches black, but after a little bore cleaner and a few strokes with a nylon brush, patches come out clean and I don't ever see any evidence of copper fouling.

So before you go shopping for bulk Q-tips and some KY jelly, think about Moly coating as a seating lube. Works for me.

 

[fguffey]

I am the fan of bullet hold; I want all the bullet hold I can get. And then there are factors, and .002” is not tension. My bullet hold is measured in pounds, I would measure tension but I do not have a gage that measures tension and no one has a conversion for tensions to pounds. All of my tension gages are calibrated in pounds.


F. Guffey

 

[RonAKA]

I use a nylon bore cleaning brush dipped in pure dry graphite to clean/lubricate the ID of my necks.

 

[ireload2]

In physics, tension describes the pulling force exerted by each end of a string, cable, chain, or similar one-dimensional continuous object, or by each end of a rod, truss member, or similar three-dimensional object.

Tension is the opposite of compression.

What is bullet hold? Define it?
What are factors?
If .002 is not tension then define what you think it is?

Did you ever use one of these with your shop skills? It is called an Instron machine.
They are use to conduct tensile and compression tests of materials and prototypes.
Notice that word tensile. Tensile means tension. https://en.wikipedia.org/wiki/Tensile_testing
That means the machine can measure the force that it takes to pull things or materials apart.
As in tensile testing. You could use this machine to measure what you call bullet hold, what some people call bullet pull and others call neck tension.
I can assure you that a tensile (tension) force of 20 lbs is exactly the same as a compressive force of 20 lbs but it is in the opposite direction.
You could measure your bullet hold by pulling the bullet out of the case with a tensile (tension) force or by pushing the bullet deep with a compressive force.
Which do you prefer and does either method really duplicate forcing the bullet out of the case with compressed gas? Since the case expands it may lose some of your bullet hold long before the bullet ever moves.
BTW these machines are calibrated by to the NIST or what used to be called the NBS. Since you are a fan of standards I am sure I do not have to tell you what the acronyms mean. You might want to learn the difference between the term calibrated and the measuring unit increments on a force scale.

I am the fan of bullet hold; I want all the bullet hold I can get. And then there are factors, and .002” is not tension. My bullet hold is measured in pounds, I would measure tension but I do not have a gage that measures tension and no one has a conversion for tensions to pounds. All of my tension gages are calibrated in pounds.


F. Guffey

 

[dkhunt14]

I like most of your post. The only thing is if the brass expands much before the bullet moves, the PPC benchresters and others would not be able to tune by going tighter on bushings. I know a lot that tune that way including 1000 yard benchresters. Matt

 

[fguffey]

I like most of your post.

Thank you, many years ago there was an Indian that no one liked, his people put him on trial, he lost; the elders told him that should tell him something, they reminded him he did not get one vote. The old Indian informed the elders he won because when the trial started every one was against me, at the end of the trial one voting member had doubts.

Again, there are factors. I do not have one rifles that will allow the bullet to leave before the neck expands, it has something to do with time and speed. I can reduce the clearance between the chamber neck and case neck to reduce neck expansion. The one thing I will not do is prevent the neck from expanding. I am the fan of bullet hold, I want all the bullet hold I can get, I want the neck to expand and seal the chamber with the neck of the case, if I get real cute with my loading I can get 'black neck'; black neck means the neck of the case did not seal the chamber. I can cut down on the time it takes for the neck to expand etc. etc..

F. Guffey

 

[ireload2]

You really should check with the Instron Corp. They have been in business since 1949 and could get your straightened out on tension testing and the definitions used.

Tension Test

A tensile test, also known as tension test, is probably the most fundamental type of mechanical test you can perform on material. Tensile tests are simple, relatively inexpensive, and fully standardized. By pulling on something, you will very quickly determine how the material will react to forces being applied in tension. As the material is being pulled, you will find its strength along with how much it will elongate.

http://www.instron.us/en-us/our-company/library/glossary/t/tension-test


I have a rifle that I shoot case bullets in that does not expand when fired. It can't the loaded round is a line to line fit at the neck and the round has to be forced home with with my thumb. When fired the cases still look new. There is zero soot on the outside.

etc etc etc does not mean a whole lot does it....

Thank you, many years ago there was an Indian that no one liked, his people put him on trial, he lost; the elders told him that should tell him something, they reminded him he did not get one vote. The old Indian informed the elders he won because when the trial started every one was against me, at the end of the trial one voting member had doubts.

Again, there are factors. I do not have one rifles that will allow the bullet to leave before the neck expands, it has something to do with time and speed. I can reduce the clearance between the chamber neck and case neck to reduce neck expansion. The one thing I will not do is prevent the neck from expanding. I am the fan of bullet hold, I want all the bullet hold I can get, I want the neck to expand and seal the chamber with the neck of the case, if I get real cute with my loading I can get 'black neck'; black neck means the neck of the case did not seal the chamber. I can cut down on the time it takes for the neck to expand etc. etc..

F. Guffey

 

[ireload2]

I like most of your post. The only thing is if the brass expands much before the bullet moves, the PPC benchresters and others would not be able to tune by going tighter on bushings. I know a lot that tune that way including 1000 yard benchresters. Matt

I just threw that in because I don't know if the variations affect time or force or both.
I shoot a few rifles with huge amounts of neck clearance -.014 and I shoot one with zero clearance.
I actually have to size the loaded round down .001 to get it to chamber, but it is a cast bullet round.

For those that tune with bushings, are they tuning velocity, pressure rise, vertical dispersion or something else?

 

[mikecr]

Bullets are not pushed out of necks. They are released from necks via neck expansion.
Don't muddle up hoop tension(that gripping a bullet) with friction(that affecting only seating forces).
That instron metal stretcher/compressor is useful to learn about tension in general, but useless for our situation.
And don't confuse interference fit with tension. It's in no way the same thing.

Bullet grip is provided by the tension of spring back against bullet bearing, and brass spring back at necks is not 5thou.
The most I've ever seen is ~1.5thou(total), and that's only with additional tension added to normal spring back against bearing, provided by sizing length beyond seated bearing(like FL sizing of necks). In this case the undersized, unexpanded portion below bearing is pulling necks hard into base-bearing junction. Yes that's more grip, but at the expense of greater tension variance, especially where there is any donut involved/sized. With an underbore(like 6ppc, 30br, etc.) relying on a very high pressure node, tension variance may not carry a big price. In fact the tune provided might completely override in results. But in any other situation FL sizing of necks can only be a detriment to results. There is nothing 'good' in it.

Where you normally partial neck size, this length is within seated bearing. Tension here is provided/adjusted by the length of normal spring back against bearing. Normal spring back is just under 1thou.
Here, a caused interference fit beyond 1thou is excessive, and a seating bullet will just finish the expansion under heavy seating force. And if your interference fit is 5thou, or 10thou, it makes no difference because the bullet will just expand the neck to where it should be to begin.
You can reduce the seating force with lube, but this changes nothing other than seating force. Folks, this does not change tension. You could clean necks to squeaky, greatly increasing seating force, and again it means nothing to tension(bullet grip).
Try it. Shoot friction differences, and partial NS interference differences across a chronograph, it makes no difference.
With partial neck sizing the only time interference makes a difference is when you've left less than full normal spring back against bearing. All of this is good for us.

Bushing die makers suggest bushings to provide for (-)2thou of loaded necks, and a follow-up with hardened pre-expansion. This should put interference ~1thou under cal. Perfect.
That 2thou under will spring back outward to ~1thou, and then expansion will drive a bit of thickness variance outward and necks will then spring back inward to ~1thou.
If the loaded ammo is not fired immediately, the necks, biased inward, will continue to spring back over time -inward(if allowed), until reaching it's lowest energy balance. That's what's happening there. Grip goes up over time.

The only way to roughly correlate tension with seating force is to exactly control friction(removing it as a variable).
I may have tried them all, and I'm convinced that the carbon layer provided in firing, is the most consistent we'll ever see.
I think that if the carbon layer was not automatically provided, someone would be selling it to us by now.

 

[dkhunt14]

Where you normally partial neck size, this length is within seated bearing. Tension here is provided/adjusted by the length of normal spring back against bearing. Normal spring back is just under 1thou.
Here, a caused interference fit beyond 1thou is excessive, and a seating bullet will just finish the expansion under heavy seating force. And if your interference fit is 5thou, or 10thou, it makes no difference because the bullet will just expand the neck to where it should be to begin.
You can reduce the seating force with lube, but this changes nothing other than seating force. Folks, this does not change tension. You could clean necks to squeaky, greatly increasing seating force, and again it means nothing to tension(bullet grip).
Try it. Shoot friction differences, and partial NS interference differences across a chronograph, it makes no difference.
With partial neck sizing the only time interference makes a difference is when you've left less than full normal spring back against bearing. All of this is good for us.

.

A chronograph will not show anything. That's why they can throw charges for a PPC and still shoot good at 100. But differences in sizing and different bushing sizes will show up on paper at 100. It shows up even more at 1000. Matt

 

[mikecr]

A chronograph will not show anything. That's why they can throw charges for a PPC and still shoot good at 100.

Here we're into a pressure node that represents a huge work-around for many things. But it's a plan that is not viable for but a handful of cartridges.
A condition you couldn't even dream for in a 243win capacity or larger.

But differences in sizing and different bushing sizes will show up on paper at 100.

I didn't mean to imply that it doesn't show up, especially given the competitive edge that PB BR goes to. It's just that diminished returns also provide diminished affects, which will never be viable in 1kyd BR.

It shows up even more at 1000.

1kyd shooters better mind their powder measure, and pretty much everything else, including actual neck tension(which will show up on a chronograph for them). If their endeavor is to reach consistent performance, it won't hurt to understand the differences I'm pointing out.
If your 5thou under cal partial neck sizing isn't showing up on a chronograph, it's because the 5thou isn't contributing to tension(just as I described). It's merely excess interference fit, removed with bullet seating expansion.
You can see this with loaded neck measure, then pull the bullet & remeasure what the neck springs back to. That difference is your tension(bullet grip),, it's ~1thou, NOT ~5thou.

 

[fguffey]

Bullets are not pushed out of necks. They are released from necks via neck expansion.
Don't muddle up hoop tension(that gripping a bullet) with friction(that affecting only seating forces).
That instron metal stretcher/compressor is useful to learn about tension in general, but useless for our situation.
And don't confuse interference fit with tension. It's in no way the same thing.

I have no ideal who is the benefactor, I said there are reloaders that do not understand there are factors, I said two factors that should be considered when the bullet is released is time and pressure, I also suggested reloaders purchase a book by R. Lee about modern reloading, after that I suggested the reloader read the book after purchasing.

Reading R. Lee's book? I said R. Lee in his book claimed he did not test Federal primers because Federal did not donate primers to be tested.

F. Guffey

 

[sfldiver]

In physics, tension describes the pulling force exerted by each end of a string, cable, chain, or similar one-dimensional continuous object, or by each end of a rod, truss member, or similar three-dimensional object.

Tension is the opposite of compression...

Did you ever use one of these with your shop skills? It is called an Instron machine.
They are use to conduct tensile and compression tests of materials and prototypes...

Thanks ireload2 for the walk down memory lane! It's been almost 30 years since I used a similar machine in my Materials Lab at the U of Miami while working on my Bachelors in Civil Engineering! And since I went into a different career(s) a couple of years after graduating, here I was thinking I'd never need any of the information I learned by compressing, pulling, twisting and flexing different materials with weird machines in that lab! LOL!!

 

[fguffey]

Thanks ireload2 for the walk down memory lane! It's been almost 30 years since I used a similar machine in my Materials Lab at the U of Miami while working on my Bachelors in Civil Engineering! And since I went into a different career(s) a couple of years after graduating, here I was thinking I'd never need any of the information I learned by compressing, pulling, twisting and flexing different materials with weird machines in that lab!

sfdiver, do you remember seeing a gage that was calibrated to tensions in the lab at the at the U of Miami? I have tension gages, all of my tension gages are calibrated in pounds, I have deflection gages that can be measured in thousandths and converted to pounds as in measuring deflection in thousandths when weight is applied. And then there is the interference fit and crush fit.

I suppose we need someone to come up with a liquid filled bullet with a pressure gage attached.

F. Guffey

 

[BoydAllen]

All of this is demonstrable by a much more direct method...results on targets. If I change a load in some way and that makes a difference on targets, then the change had an effect. Whether we properly understand, or agree upon the exact mechanism or not. When I change the difference in diameters of loaded necks and sized necks targets show a difference.

One thing that seems to be missing from most discussions of the effects of "neck tension" (difference in sized and loaded neck diameters) is the step in the neck, at the base of a flat base bullet that has been seated. For those situation where bullets are seated to an interference fit with the origin of the rifling (some length beyond touching) the maximum to which the bullet may be seated before chambering the round in which it is loaded will move it is affected by "neck tension". A simple experiment will demonstrate this.

In short range benchrest, as with longer range, accuracy nodes may be defined as a range of velocities that, all things being equal, can be associated with a range of charge weights. If our charges fall outside of that range, the result will show up on targets. Nodes have width, and some powders, based on the size and shape of their grains, are easier to throw staying within node widths than others. Measure technique is another variable. As with shooting, proper selection of technique and the skill with which it is employed will affect results. If we use thrown charges, a chronograph may help explain why a shot went astray.

A significant number of skilled short range shooters have convinced themselves that weighing charges gives better results than throwing them, especially if the powder is difficult to throw consistently. As with many thing the sport has changed over time.

 

[mikecr]

I suppose we need someone to come up with a liquid filled bullet with a pressure gage attached.

A stationary hydraulic expanding mandrel with a pressure gauge plus an indicator combined to show us the PSI needed for 1/2thou of neck expansion for .xxx of neck length. This would not tell us actual bearing seated grip, but would be a far better comparative measure than correlated seating forces.
The difficult part is the expanding mandrel design.