Neck Tension

[gunsandgunsmithing]

Mike, I think we have talked about that before where no single point of wind takes a right hand twist high right or low left.
When I’m testing I really don’t try and correct for wind , rather make a note of the conditions to help understand the rounds went flat or vertical or just plain weird.
Wish you lived closer I could learn a ton from you.

I wish you lived closer too. I'm sure I'd learn from you, as much if not more. If nothing else, we could burn some powder and shoot the breeze

 

[Timon]

I think that to truly control neck tension, you have to turn the necks. That gets it about as good as it can get. If you don’t, you’re really just playing with fire that the tension will be consistent. I use all Lapua brass, but there is still inconsistencies in the neck thicknesses. Slight, but they are there. Turn the necks and take them out. I use the 21st Century lathe. It’s really quite easy and fast.

 

[Clancy]

Don't know what discipline you are shooting , but most every F-Class shooter I know takes the subject of Neck Tension very seriously , since most also "jump" our bullets , from as little as .005 to what-ever works in "THAT" barrel . Powder load to group , Seating Depth , and Neck Tension . But most F-shooters start with .001 - .002 .

Great. I’m confused. All I did was point out that he asked about variations in neck tension, not how much tension he should use.

 

[D-4297]

Great. I’m confused. All I did was point out that he asked about variations in neck tension, not how much tension he should use.

My comment had absolutely nothing to do with anything you posted . a Maybe I should elaborate . Your question was in relation to testing , and I guess I wasn't clear enough , that most F-Class guys do extensive testing of neck tension , and seating depth , and in no way was I trying to say there was a good or bad set-up . Just starting points . I've probably shot 2,000 rounds . doing nothing but testing neck tension in the last five years . I do neck tension tests when I change lots of powder . Sorry if I wasn't clear enough in what I was trying to say !

 

[mikecr]

The amount of the interference fit between the bullet and the case neck is commonly referred to as "neck tension". I do not think that is the best technical term, but I will use it here to help with communication.

You know it's interference, and you know it's not tension, as neither tension nor force are expressed in inches. Seating force is not tension either, but a matter of friction that is only partly due to tension.
Also consider that we currently have no way to measure tension -because we don't.

I mention these things because they really sum to prevent solid answers (that pass all tests).
Our tension (what grips bullets) is hoop tension. It manifests as a springback force against an area of bullet bearing, and binding at the base-bearing junction if sizing length exceeds seated bearing.
The area is set by the cal and chosen sizing length. The spring back force is set by brass hardness, thickness, and interference within modulus of elasticity.
These are the things to consider when managing consistency.

As far as whether it matters?
There are conditions where it doesn't, and where it does.
For my hunting capacity cartridges, seated off the lands (OTL), I have adjusted tension with neck sizing length, while interference is set at 1thou as my standard. This is a super fine adjustment though, which is easier to cover with kernels of powder. Given that, for the past couple cartridges I have simply chosen half neck sizing length and 1thou interference. With tight clearances, and this minimal sizing, and initial dip annealing, I feel confident that my tension is very consistent.

I do check pre-seating forces with an instrumented mandrel die. Every case, every reload.
With this I can see outliers, adjust them (through sizing length), and I can see when the batch is due for another dip. I keep necks normalized in friction by leaving the carbon layer alone.
That's the best I can do for now.

 

[Larry Koch]

I don’t turn necks unless I have to, I prefer to set my no turns up with .004 clearance.

That’s why I set my tension with a mandrel. I size down .004 below and then run a carbide mandrel that’s .001-.003 under, usually .002 unless it’s not satisfactory. This does a decent job of uniforming tension and it most definitely shows on paper.

When I do have to turn, I still turn for .004 clearance and size the same way, which makes tension as uniform as it’s ever going to get.

I have tested freshly annealed cases with and without turning and with and without the mandrel and the improvement is definitely linear in a positive direction the more steps I take.

I want good clearance, imperfections on the outside or nonexistent and low (but not too low) seating force.

People have been turning to the .0001 and annealing for decades. I think that’s many a thousand “ayes” for uniform neck tension.

In addition to that, check out some groups fired from custom muzzle loaders. They will all shoot in the .1s. Why? The absence of a case screwing things up is my opinion.

Bottom line, absolutely anything or everything you can do to make one case exactly like the other 4 in a string is going to show on paper. Uniform neck tension is near the top of that list.

The amount of the interference fit between the bullet and the case neck is commonly referred to as "neck tension". I do not think that is the best technical term, but I will use it here to help with communication. So, using this definition, If I seat a 0.224 diameter bullet in a case with an internal neck diameter of 0.221 the result is 0.003 neck tension.

I have measured the expander ball on my standard Remmington 223 case resizing die and it is 0.223 and this gives me 0.003 or more neck tension depending on the spring back of the brass. With neck tension at 0.003 or greater it takes what I would subjectively judge to be considerable force to seat the bullet in the case. I have concerns that this level of force may do some damage to the bullet and may be detrimental to accuracy.

I have found that I can control neck tension by the use of the proper diameter expander mandrel. There are now good sources of expander mandrels in measurement increments of 0.0005 and with a little experimentation I can set neck tension at the amount I choose within the limitations of the variation of the spring back of the brass. This helps reduce the seating force and gives a much more consistent feel during the bullet seating process.

For a semi auto like the AR it is not recommended to go too low due to the risk of the bullet moving in the case during the dynamics of recoil and of the cycling of the action. So, I set neck tension between 0.002 and 0.003 for that application. For the single shot bolt action, I set it at approximately 0.001.

My question is, has anyone done any accuracy testing to see if there is any effect on accuracy due to variations in neck tension?

Yes, Neck tension, makes a difference in accuracy. Some powerders are more forgiving than others. You have to start with quailty brass, like Lapua.

 

[durand mortenson]

Great reply, thanks. I too bought bushings and mandrels of various sizes and they allow me to control neck tension very well but it is somewhat tedious especially with the variation in brass spring back. I would like to know if the effort is buying me anything in accuracy.

Do you have any accuracy vs neck tension data you would like to share?

Thanks again for you reply.

I don't worry about spring back .I neck turn and resize before measuring inside the neck with an adjustable inside ball micrometer. These are avalible from Starrett..

Mort

 

[JFrank]

I’m testing bullet hold differently these days by following the lead of some other LR shooters, a guy may not even notice the difference at short range but at longer range mine has a pretty clear preference.

 

[gunsandgunsmithing]

I want to be clear about something that I'm seeing a lot of lately. Moa is moa. The difference is more apparent at longer distances but groups don't get smaller at longer distances and wind makes it harder to distinguish changes as yardage increases. It might upset or rub some wrong and it's certainly not said with that intention but...short range BR is still the pinnacle that proves things out more than anything else. If it matters at 1000, it matters at 100 too, but just doesn't show as clearly. Thing is, it's all relative. So whether it's .010 or .100, it's the same change in accuracy potential. The only difference is the value of wind, which is not the same thing. Accuracy changes are moa changes where precision changes, to me, are about hitting what you're aiming at and are related to precision. Not sure if I have the accepted defintions right or backward but it doesn't change my point.

That point can be summarized by wind and its larger value over distance being essentially a square root function vs accuracy being strictly doubling of the group size when yardage is doubled.

Both short and long range shooting are very demanding of shooters, their equipment and their loading. But being further away from the target gives a better assessment of the shooter error vs short range being a better measure of tune and equipment, simply because wind has more value over distance than does inaccuracy of tune and equipment.

So if I say I have a .2 rifle, that should be true ant any yardage. Since match results reflect that a large percentage of shooters and equipment are .2 or below, yet there are literally zero in long range, reflects this as well. Just saying...and yes, there are variables. Yes, a short range setup will seldom hang in long range matches...The two are very different games but how we define accuracy doesn't change. If it's .2@100 it's.2 moa at 1000, without wind.

Bottom line, both take extreme levels of skill and equipment performance but one should not discredit what works at one vs the other entirely. The less influence wind has, the better the test results, overall. I'm not badmouthing any discipline. What I'm saying is almost common sense, IMHO. My main point is that if you want to see if changes help or hurt the gun/load, shorter range eliminates more condition related changes that we can't generally control.

Just be honest with yourself when evaluating any changes and test them thoroughly at both short range, confirming at long, if that's your discipline. Just don't be fooled by results at long range that aren't supported at short. Common sense tells you that long range is more condition dependent. That's really all. I don't want that to upset anyone and if you're realistic about how you test, it won't upset you. Because it's reall just common sense stuff.

 

[JFrank]

Mike, if you posted that for my benefit I thank you. I’m comfortable with the distance I’m testing at and I’m comfortable with the results, including interpreting conditions, when I test at short range everything looks the same, and still gets confirmed at long range. For those that can tune a 1/4 minute load at 100 yards and have that translate to 2.5 in LG groups at a 1000 yards, i tip my hat and congratulate. Those kind of groups are rare.

 

[Alex Wheeler]

In my personal experiance I cant get my long range tune at short or midrange. Until you do it and see how things change with distance you just wont understand.

 

[gunsandgunsmithing]

Mike, if you posted that for my benefit I thank you. I’m comfortable with the distance I’m testing at and I’m comfortable with the results, including interpreting conditions, when I test at short range everything looks the same, and still gets confirmed at long range. For those that can tune a 1/4 minute load at 100 yards and have that translate to 2.5 in LG groups at a 1000 yards, i tip my hat and congratulate. Those kind of groups are rare.

You did say something(I forget what now) that prompted me to say this but it wasn't so much pointed at you as it was just pointing out the common sense aspect of it. I suggest my tuner test be done at 100 for the same reason. It does the same thing at longer ranges but it's just harder to trust and interpret the results is all. That's just a good example of moa and the test is strictly about seeing the effect of the tuner, not about the final tune. No, I certainly didn't mean to step on your toes and hope I didn't. It's just about trusting every shot during that test.. and as distance increases, wind is a bigger, proportionally, factor. That's all I'm saying. I don't know anyone that can read the wind at 1000 as well as they can at 100. Like I said, it's just about common sense. Not that one is better or harder or any of that. And you might end up a mark away from what your best setting is at 100, at 1000. It's very little or no different, if done in the same conditions, though.

 

[JFrank]

I’ve always liked you and respected your input, you try to stay polite yet straight forward. That’s cool not everyone is like that. Im probably a bit sensitive today, but that’s a different topic. I’ve spent the last five years working on a tuning style that suits my shooting discipline so I doubt I’ll change much now.
I can’t comment on tuners, I wouldn’t even know where to start.

 

[gunsandgunsmithing]

I’ve always liked you and respected your input, you try to stay polite yet straight forward. That’s cool not everyone is like that. Im probably a bit sensitive today, but that’s a different topic. I’ve spent the last five years working on a tuning style that suits my shooting discipline so I doubt I’ll change much now.
I can’t comment on tuners, I wouldn’t even know where to start.

Man, we're good, I hope. Yes, I do sometimes step on toes, even by accident in type. I try, but it's just who I am. I'm better in person or on the phone, I think. Anyway, thanks for the kind words and I'm always happy to help where I can. --M

 

[tom]

I like to do it like Jim posted on target rifles, where I can compare the entire ladder vs just looking at any one group. Hunting rifles, a guy is stuck doing a group at a time, and that's fine, but may take more range trips to see repeatability is all.

Tom


Mike, you should chat with a guy that has a personal 1k range and multiple e-targets......eye opening! Not me, I'm still using the woods, and sharpies lol. That knowledge is out there, but not my data to share.

Tom

 

[gunsandgunsmithing]

I like to do it like Jim posted on target rifles, where I can compare the entire ladder vs just looking at any one group. Hunting rifles, a guy is stuck doing a group at a time, and that's fine, but may take more range trips to see repeatability is all.

Tom


Mike, you should chat with a guy that has a personal 1k range and multiple e-targets......eye opening! Not me, I'm still using the woods, and sharpies lol. That knowledge is out there, but not my data to share.

Tom

Which data are you referring to Tom? You can use pm if you prefer.

 

[L.Sherm]

Not me, I'm still using the woods, and sharpies lol.

Some of us its hard to take the woods out Tom. LOL
Were im at now not many trees so I kinda miss the woods but it does have a nice range to 900.
When I do go though I go at the ass crack of Tom so I have it to myself LOL

 

[tom]

Some of us its hard to take the woods out Tom. LOL
Were im at now not many trees so I kinda miss the woods but it does have a nice range to 900.
When I do go though I go at the ass crack of Tom so I have it to myself LOL

You'd still be late!

 

[JFrank]

I’m surrounded by Black Bear that time of morning. They like to eat old people..

 

[rjtfroggy]

The original question was to decrease neck tension, but what if you need to increase the tension? Use a smaller bushing, new custom die, or what??
Reason for question is I'm changing bullets from 115 Berger's to 118 custom made and have no grip (tension) at all. Different ogive and about 0.033 longer at ogive. Dropped down one size on bushing no change in tension, loosing what little hair I have left figuring this out, probably a simple fix just not hitting it yet.