Neck tension

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joeb33050 posted this 03 April 2015

            I got TFS No. 234 Monday, and read it all, including Tom Acheson's article on case neck tension.             Wednesday I went to the Trail Glades Range in Miami. There was a new serious benchrest shooter there; there have been less than half a dozen serious benchrest shooters there, when I was there, in the past 14 years.             A serious benchrest shooter is easily identified; he has a rifle that others stop to look at, a powder measure, and an arbor press. This guy was shooting a .20/223, sort of a .204 Ruger.             An hour into shooting he came over, looked at my rifle and lead bullets, and began to talk about neck tension and accuracy. He didn't say “neck tension”, but he described the varying force required to neck size, to expand necks and to seat bullets. He explained about the need for exactly equal case lengths, for turning necks, for measuring turned necks and segregating cases by neck thickness variation-or discarding nonconforming cases. He explained about his equipment for trimming, turning and measuring case necks, the perils of the “doughnut”, what work hardening is, annealing and his annealing machine.             He told about the better benchrest shooters and the 1000 yard guys, how they were absolutely and universally convinced that necks were crucial, and that they annealed after every firing. He said that he sometimes went as many as three to five firings between annealings, but intimated that annealing every time was best. This accompanied by recurring explanations of work hardening, in case I'd forgotten.             Now this guy was sincere, he had the gun/s and equipment indicating that he was serious and knowledgeable, and he's a fiery-eyed zealot/proselytizer about neck tension.             The man probably said a lot more, but being deaf as a haddock I missed it. This was not a discussion, questions were not allowed, it was a sermon.             My position on neck tension is that I throw out any case with unusual force required to size, expand necks or seat bullets. I keep cases together by lot, starting with ~120, shoot them in order so each is fired ~ the same number of times, and anneal all when the first neck splits. My cases last a long time, many firings.             I don't have an opinion on neck tension vs. accuracy; the TFS has articles with conflicting conclusions. But I now know someone else with a firm opinion.      

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billwnr posted this 03 April 2015

I like uniform neck tension were every bullet seating feels the same.

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OU812 posted this 03 April 2015

I seem to load more concentric ammo using less neck tension and turned necks. But I have no proof these cast rounds shoot more accurately. There is never enough range time for me.

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Maven posted this 03 April 2015

I don't have a horse in this race, but it seems to me that John Alexander's suggestion (last paragraph, in italics, on p. 234-24) is worth implementing.

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Tom Acheson posted this 03 April 2015

If there was no neck tension would the bullet fall onto the top of the powder column? Otherwis if it doesn't then neck tension exists, yes/no? Probably becomes a case of sliding fit to interference fit or somewhere beyond that.....

Tom

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joeb33050 posted this 04 April 2015

Tom Acheson wrote: If there was no neck tension would the bullet fall onto the top of the powder column? Otherwis if it doesn't then neck tension exists, yes/no? Probably becomes a case of sliding fit to interference fit or somewhere beyond that.....

TomI think that there's no neck tension with breech-seated bullets, and we've seen the good accuracy with these. As explained here in the past, I shoot semi-breech-seated bullets in 30-30, 45-70 now, have done for years-these and other guns. Push the bullet in, put the case in, neck around but not holding the bullet. Forgot the 32-35, same semi there.Works for me. Does no-neck-tension make these guns accurate? I don't know.I use the method because I don't have bullets that will breech seat all the way. 

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joeb33050 posted this 04 April 2015

I keep looking at Tom's article in TFS 234 on neck tension. If I understood and copied the numbers from the article correctly, there were (16) 10/200 groups shot in Season 1 and (14) 10/200 groups shot in Season 2. All otheer averages are of (4) groups.The SHOTS/RANGE YARDS, group averages and percent average group size reductions are copied below.   10/100, 1.689” TO 1.496”, -11% 5/100, 1.325” TO .6785”, - 49% 10/200, 4.226” TO 2.011” ”€œ 52% 5/200, 3.209” TO 1.605”, -50%     I don't know if neck tension affects accuracy, but I have a very strong opinion that reducing the neck sizing bushing ID by .001”-.002” which sizes the neck smaller and increases neck tension will not reduce group size anything like 50% as this data suggests. Either there's a statistical williwah happening or something else changed, or both.        If my opinion is incorrect, then anyone with the appropriate neck sizing dies/bushings could demonstrate this large change in a few hours shooting and open up a new path to accuracy. 

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Tom Acheson posted this 04 April 2015

Joe,

There is one component missing.....me. Even though these groups were shot under match conditions, not cherry picked weather, every time you sit down behind the bench you the shooter are a different person. This isn't a science and we aren't machines so our results will vary. But how do you graph that? What factor do you apply to “normalize” the results?  Maybe it's a lot like fishing. You go to the lake and see what happens. There are some things we just can't control. We can influence them but not fully control them. And this is an XP-100 not a Unristricted pistol. The max weight is 7-pounds, not any weight you want. And you have to have consistent grip pressure from shot to shot. This thing jumps and twists during recoil. The consistent grip pressure is one thing I really struggle with. Somedays it works and somedays it don't work as well. And that's why they call it fun....you just never know....

Tom

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John Alexander posted this 04 April 2015

joeb33050 wrote: If my opinion is incorrect, then anyone with the appropriate neck sizing dies/bushings could demonstrate this large change in a few hours shooting and open up a new path to accuracy. 

Finding some answers by a few hours of testing is something that could be done not only for neck tension but also for a lot of other cast bullet casting and loading procedures that are based on opinion, conventional wisdom, and flawed logic -- but not on facts found by testing.      As far as neck tension is concerned, an excellent test has already been done even though the results seemed to have been ignored.  Gerry Bottiger reported in the 2013 July/Aug. Fouling Shot (#22) on a well designed series of tests he did to see how much influence neck tension had on velocity and accuracy.  He found absolutely no difference in either based on neck tension.  

There has been some doubting and theories suggested since Gerry's article was published to try to claim neck tension does make a difference but no test results to challenge Gerry's results have been offered.  

Gerry's tests were conducted with a rifle and load shooting approximately 0.5 MOA for five shot groups. If no effect could be shown for different neck tensions at this level of precision it is not likely that it affects the results of folks like me averaging 1 MOA on a good day.

John

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TRKakaCatWhisperer posted this 04 April 2015

Tom Acheson wrote: If there was no neck tension would the bullet fall onto the top of the powder column? Otherwis if it doesn't then neck tension exists, yes/no? Probably becomes a case of sliding fit to interference fit or somewhere beyond that.....

Tom
Sort of, generally. To reduce the influence of variations in neck tension WHILE reducing the variation of location of the bullet (axial alignment and such) I size only minimally (to keep the body of the case as close fitting to the chamber as functionally possible and then expand for a specific DEPTH and DIAMETER that allows the bullet to JUST slip into the case and stop at a consistent place.  It is close enough in diameters that when the bullet is lubed there will be enough resistance to movement provided by the lube to keep the bullet in place during handling.  

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Tom Acheson posted this 04 April 2015

This may not be germain but the dimension of the neck in the chamber is 0.332” and a loaded round (Lapua cases, neck turned) was 0.331” OD. So there is very little clearance once a round is chambered. If I recall correctly, the bullets were seated about 0.025” too long and closing the bolt pushed the bullet back into the case, at the same time being engraved by the rifling and (hopefully) centered in the chamber. I suspect that changes in bullet hardness would influence the amountof of bullet travel when closing the bolt. The alloy in many situations was 50/50 lino/mono and the bullets were “bumped".

But.....that short article at least got a few of you offering opposing views which is what I was hoping for. I need all of the research I can get to try to get this new chambering (30/223) to shoot like the 30 PPC.

Thanks guys!

Tom

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billglaze posted this 22 April 2015

I hope this might be of some interest in this neck tension discussion. I believe this story originated with Phil Sharpe, but I can't say for sure. Many years ago, the Gov't was having trouble with copper fouling in the service rifle. (Springfield, I believe.) So, after experimenting, they discovered that alloying the copper with tin greatly reduced the fouling. Some years later, they began to have trouble with rifles being damaged/destroyed by what seemed to be excessive over-pressure. They investigated the ammunition by pulling the bullets, and checking powder quantity, instability, etc. You can imagine the drill. Finally, someone suggested checking the bullet pull, which, as I recall, was specified as 35 lbs., plus a nominal tolerance. To their amazement, the tensiometer showed some rounds with a pull of over 200 lbs. It developed that the tin used in the alloy had caused the bullets in some cases, to be actually soldered to the case mouths. So, they changed to an alloy containing Nickle, which solved that little problem. While slightly off-subject, I hope someone finds it interesting. Bill

In theory, there's no difference between theory and practice. In practice, there is. My fate is not entirely in Gods hands, if I have a weapon in mine.

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John Alexander posted this 22 April 2015

Thanks Bill I found it interesting and I'm sure others will. Soldered in bullets are probably not a good thing.  As long as the subject of neck tension has come up I should say that I have corrected post #9. The fouling shot that refers to Gerry Bottiger's article on the subject. It is in TFS #224, July-Aug. 2013 - not where I originally said it was.

Anybody who thinks variations in neck tension affects rifle accuracy should read this article -- and then read it again. Gerry reports on a well designed test where two sets of loads were as identical as he could make them with the exception of neck tension and groups of each were shot alternatively in the same conditions while comparing velocities and group sizes.

The neck tensions in one set of loads were almost twice the neck tension in the other. Yet Gerry found no significant difference in either velocity or accuracy and since accuracy for Gerry and this rifle means averaging .5 moa we should think about that. 

Theory often leads us astray so we should be skeptical but maybe a little theory might be helpful for those that find it hard to believe that neck tension doesn't have any effect on velocity or accuracy in a rifle.  The two seating forces in Gerry's ammunition were approximately 30 and 60 pounds which are typical.  It may be helpful to consider that while the bullet is being urged out of the case neck by expanding gas, the force (pressure x area) on the bullet base is in the neighborhood of maybe 2,000 pounds or more. Considering how tiny neck tension is compared to the pushing being done it doesn't seem so amazing that changing from 30 to 60 pounds of seating pressure has no measurable effect on anything important.  Difference in neck tension are simply in the round off error of the 2,000 pounds which is varying from shot to shot far more than the 30 pound difference in neck tension. 

Of course rough estimate above of the forces involved assumes there is any neck tension when things go bang.  Maybe the first thing that happens is that the pressure expands the neck before the bullet moves much leaving the rear of the bullet hanging in air with no neck tension at all.

John

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gpidaho posted this 23 April 2015

I think everyone here can safely assume I don't know what happens at the moment of ignition, but as far as neck tension goes I believe the last sentence of John A's post seems most likely. GP

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Newt posted this 05 February 2016

I was going to start a thread asking how many guys on here turn necks on their brass......but I think I get the idea from reading this thread.

I had never contemplated neck turning, thinking it to be only for the guys wanting to shrink groups by a few thous to beat the next benchrest guy, but there is one aspect of it that I wonder might help the “average” handloader.

I sometimes have a horrible time with seating my bullets straight. I can do all the prep on the cases the same way - cleaning, sizing, flaring the mouth, etc - and take care of how I seat, but still wind up with some that are just a little out of concentric with the case.

I do not have a factory made tester to see this which makes it worse because I can see it with just my eyes(I do have a homemade spinner). I can also see the results when I sort the bad ones from good ones and shoot them.

I have gotten better results since I started using the Hornady seating die with the floating sleeve, and I have some expanders coming from NOE that are supposed to work like the Lyman M type. I have to wonder if this is where I will see my largest improvement in concentric rounds. Can anyone say that they saw a dramatic increase in consistency when they started using a good expander over the standard expander in a die and then just flaring the case neck?

So for me, the thought of neck turning wasn't so much about bullet pull/tension as it was how it might effect bullet seating and the bullet being straight inline with the bore each and every shot.

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highstandard40 posted this 05 February 2016

I don't have extensive test results to prove it, but it is my belief that proper neck tension and the resulting concentricity of loaded bullets are directly related. If there is excessively tight neck tension, it stands to reason that it can cause issues when seating a cast bullet which is much more malleable than a jacketed bullet. I try to have .0015"-.002” neck tension. I can say that holding to this standard along with some other steps that I take in my loading process have shrunk my group sizes greatly. Since I made multiple changes at one time, it's hard for me to say how much difference neck tension made but I am convinced it is a positive step.

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R. Dupraz posted this 05 February 2016

highstandard40:

I agree with what you wrote especially the part about neck tension and concentricity being directly related. And my results have been the same.

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Newt posted this 05 February 2016

I got both of the expanding stems that NOE offers. If I am reading their sizes correctly I may have to do some modifications to one in order to make it fit right.

The expanders are labeled .226x.222 and .228x.224. I am going to guess that .228x.224 is what I will be using. I size my bullets to right around .2255". I figured I would use the other for jacketed bullets.

My plan is to take the stock expander out of the sizing die and just run the case up in it sizing the neck. Then run them through the expander to open up the necks and give that little step for the bullet to sit in while going into the sizer. My hope is that all of it combined will amount to more concentric rounds.

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billglaze posted this 05 February 2016

Newt:I used to turn necks for my 600 yd. slow fire stage of the NM Course; couldn't tell any difference in score, pro or con, but it was a pretty superficial test.  Kinda forgot about it. A few years ago, I bought a Hornady Concentricity Gauge; a very well made tool.  I found that the worst (the very worst condition) showed a few bullets to be .0015” out of concentricity; most were less than .001. So, I tried the Gauge on my cast loads; same result; a max. of .0015".  I straightened the rounds, then began wondering if I was truly straightening the round, or if, perhaps, I was, in fact, actually bending the bullet.  I still don't know, but I quit checking for concentricity as it didn't help accuracy; neither did it seem the neck turning helped.   Bear in mind that this “test” was as unscientific as it may come, and we're not talking world-class groups, either, but purely Observational convention.  Bill

In theory, there's no difference between theory and practice. In practice, there is. My fate is not entirely in Gods hands, if I have a weapon in mine.

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TRKakaCatWhisperer posted this 05 February 2016

Hmmm. 1-1/2 thousandths TIR is GOOD. You've got a grip on it Bill!

(Factory ammo runs .015 down to maybe .004 give or take; army FM lists .004 or better for 'match' ammo.)

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Newt posted this 06 February 2016

I would think .002” runout would be ok. I'm just looking to get it down as far as possible with normal tools. I am not measuring them so I don't know the exact amount. I just know that it is enough that when I separate and shoot groups the difference is very noticeable, like inches.

For those of you who do measure run out, what have you noticed made differences? I did check how the shell holder lined up on the seating die and there was a noticeable gap. So I moved it to another press that lined up near perfect far as I can tell.

Have not tried seating yet, still waiting on the expanders.

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