Adjusting Neck Tension

[hhunter318]

Okay. I shoot a lot, but one key thing I have ignored up until this point is neck tension. I'm shooting a 7mm WSM and use the Hornady Custom Grade New-Dimension dies with a micrometer on the seater die. My question is can, and if so how, do you adjust neck tension with this normal full length sizing die? Can it be done or do I need to switch over to something like a Redding bushing die? Also, I'm neck turning, so I know that comes into play.

[Jimro]

Neck tension is normally increase by using a smaller expander die, and decreased by using a larger expander die. This is done with the resizing die, not the seating die. If you have a factory chamber, there isn't much point playing round with neck tension IMHO.

Jimro

[PawPaw]

Why do you want to adjust the neck tension? If you're trying to get more neck tension, the easiest thing to do would be to chuck the expander stem into a drill press and polish off a thousandth or so.

[hhunter318]

Okay. Thanks. I understand now. I was actually talking about decreasing neck tension. But from the sound of it it sounds like that is a no-go.

[old roper]

Since your turning necks why not using a bushing die.

If you get the Redding Type S you get that standard type expander and decapping pin retainer and you use that so your not working the inside of the necks.

[F. Guffey]

Bullet hold, I am the fan of bullet hold, I want all the bullet hold I can get, I can measures bullet hold, neck tension? Again, I want all the bullet hold I can get.

F. Guffey

[hhunter318]

Okay, then forget the neck tension question. My standard sizing die is set up for neck sizing only. If I start turning the necks will I have issues as far as the neck sizing goes? I don't want to buy a new die unless I must.

[Jimro]

As long as you are turning the outside of the neck you should be ok. But once again, if you don't have a match chamber you'll see limited return on neck turning your ammo. I would uniform flash holes first.

Jimro

[markr]

One word: Lee Factory Crimp Die.

[F. Guffey]

Again, a builder/reloader/shooter of bench rest type rifles after all his effort gets one hole groups results, then someone convinced him the necks on his unfired cases were too small in diameter before firing and too large in diameter after firing, so he went on a quest to tighten his necks, and he asked me over to get involved if I thought I could solve the problem. It is not for me to ask about the effort and improvement in accuracy, accuracy can not be improved over ‘a one hole group’. I explained to him the only improvement he would see would be in case life, the expansion of the case neck would/could be reduced from .010 thousandths to .004 thousandths by forming his cases from 30/06 to 308 W if he used Surplus ammo or less if he used factory factory 30/06 cases.

I do not know the diameter of your cases after loading, I do not know the diameter of you necks after firing, I do not know the diameter of your chamber neck, thinning the neck, inside or outside would reduce bullet hold, thinning the neck would increase neck expansion, in my opinion it would make more sense to start with a chamber neck that required case neck turning or find cases with thick necks, I want bullet hold, I want all the bullet hold I can get.

F. Guffey

[wncchester]

Playing with 'neck tension' is largely meaningless for factory rifles. I won't ever say 'never' about anything in reloading but worrying about neck tension is about as meaningless as it gets. Excessive 'neck tension' only makes it harder to seat bullets and that increases the loaded bullet run out and run out is detrimental to accuracy without increasing bullet pull at all.

What gets called 'tension' is really an interferrence fit, meaning the hole is smaller than the thing we push into it. Any neck hole smaller than one thou under bullet diameter is meaningless; it seems most think the extra effort required to seat in a smaller neck surely means it grips the bullet tighter but that's not true. The extra seating effort is just the bullet having to expand the neck to get in. When the elasticity of the brass is exceeded we have all the perminant 'tension' we gonna get, and that happens with the last thousanth or so.

One of the major reasons many of us get best accuracy with the Lee Collet Neck dies in factory rifles is that die is designed to obtain a sized neck about one thou smaller than the normal bullet diameter so we get less run out; works good too. (But a LOT of guys mess it up by sanding the mandrel down too small!)

[markr]

I mentioned the Factory Crimp Die earlier, I'm suprised nobody commented because the FCD for rifles does exactly what the OP wants. It applies uniform neck tension, and is adjustable. If he is after uniform neck tension, or higher start pressures without altering his other dies, or turning case necks, etc, wouldnt the FCD be an answer?

[wncchester]

"...wouldnt the FCD be an answer? "

I love FCDs and the rifle crimper is certainly A way to obtain some bullet grip but that's really the job of the neck itself. Crimping is intended to hold the bullet in place from outside forces, which should NOT be in play with modest caliber bolt rifle cartridges.

[markr]

Not sure what you mean, because the rifle crimp die, at least the one I use for 30/06, doesn't even "Crimp" the case into the bullet, it merely applies pressure (Neck tension?) uniformaly around the case neck. Hence, increased neck tension.

[old roper]

Here something from Sinclair on turning necks

http://blog.sinclairintl.com/2009/02...actory-rifles/

[F. Guffey]

http://www.hornady.com/assets/files/...stom_grade.pdf

“My question is can, and if so how, do you adjust neck tension with this normal full length sizing die? Can it be done or do I need to switch over to something like a Redding bushing die? Also, I'm neck turning, so I know that comes into play”

“I was actually talking about decreasing neck tension”

“If I start turning the necks will I have issues as far as the neck sizing goes?”

He wants to decrease neck tension/bullet hold, so forget crimping, I am not saying I do not have FCD dies, I am saying I do not use them, then there is the trimming and crimping with standard dies, if the cases are not trimmed to the same length the crimp will vary from small/slight to crushing the case when the bullet is seated.

So, reducing bullet hold/neck tension for the sake of reducing neck tension without a rational, logic or reason is busy work. Hornady sells one sizer ball/sizer plug for the 7MM, RCBS sells one sizer plug for the 7MM, when reducing the sizer ball/plug diameter you are on your own, (keeping the story straight) to reduce bullet hold/neck tension the sizer ball/plug would have to increase in diameter, to increase bullet hold/neck tension the sizer plug would have to reduced in diameter. to complete the thought: The .223 bullet is .224 in diameter, reducing the diameter of the seater plug would make it more difficult to seat a bullet, there is a chance a flat based bullet could cause the case to crush, the seater plug diameter is .223, that is .001 thousandths smaller in diameter than the seater plug, then there are those that have increased the diameter of the die’s neck by honing and or grinding, and it goes on and on and on.

So, the answer is yes, purchase the bushing sizer dies, as for me? I have Micro Adjust seater dies in Competition and or Gold Medal for 4 chambers and I make a seater for the 25 cal anything, no dial, no indicator, no threads no die body, not for everyone. And all of my seater dies are micro adjust, when it matters, I use a modified case to transfer the measurements from the chamber to the seater die, then .000 the height of the seater plug above the die. Then use a ‘micro’meter height gage and or a dial caliper to adjust the seater stem to seat bullets to or off the lands in thousandths. And it is not like discovering American over and over, I save the transfer, and the ojive of the chamber does not change/move, on the 30/06 the ojive is between .300 and 308 and has a bevel.

F. Guffey

[hhunter318]

Thanks for the replies. I have a better understanding now. I believe I will be happy with what 'bullet hold' I currently have.

[Clifford L. Hughes]

Hhunter318:


If you are experiencing loose bullets when seating, you may be taking off too much brass when neck turning. Take off enough brass so that the thin side is only touched by the cutter.

Semper Fi.

Gunnery Sergeant
Clifford L. Hughes
USMC Retired

[frank_1947]

since your useing a FL die just buy redding Type S neck bushing die, measure your loaded round then when you order die order a bushing that is .002 smaller and .004 smaller, just do your normal sizeing the run them through the neck bushing die or it cost more but redding make a bushing FL die , either way works.

[Unclenick]

Markr,

Alas, there is no way to tighten the brass from the outside without indenting the bullet as the brass tends to spring back from applied pressure. The slight indentation is needed to give it a "hook" to hold on with. If you pull a bullet successfully crimped with the Lee die and mark the side with a Magic Marker, then pull it along a flat surface like a pane of glass, you will the marker remains where the crimp was because the bullet has, indeed, been narrowed where the die touched it. If it hasn't, you didn't have the die adjusted to give you a very serious degree of crimp.

The above was the basis of the advertising "feud" that went on between Lee and Sierra for a few years back in the early 90's. Sierra didn't want their carefully uniformed bullets indented for best accuracy, while Lee claimed accuracy was improved by their crimp which improved ignition consistency. In the end they were both right under the right set of circumstances. Under some conditions, like extreme long range shooting, the indentation's effect on ballistic coefficient made its consistency and uniformity extra critical and it could become a dominant error term over a long flight. Guys with benchrest chambers who were making perfectly uniform ammunition with good case fill could introduce bullet tilt and other issues with that crimp that a gun grouping in the tenth inch range can reveal.

On the other side of the coin, if a fellow was shooting in a wide range of hunting temperatures, the extra start pressure from increasing bullet pull could improve ignition consistency enough to get better accuracy. If he had a gun with a whippy barrel, that improved consistency could keep the bullet exit timing closer to the same phase of muzzle deflection every time. If he had a self-loader, like a service rifle, that tended to push bullets in or tip them, the crimp could help prevent that irregularity.

So, the bottom line is you have to try it in your gun. As a general rule, I think you'll find that if your gun's best groups without crimping are no better than about 1 moa, the crimp may provide help. If your best group without crimping is under 1/2 moa, it may make it worse. This happens because of the trade-offs involved.


hhunter318,

As to neck tension, generally speaking, Mr. Guffey has it right: more is better from the starting pressure and ignition standpoint as long as it's consistent. Military match ammo in a number of instances has been found to be more accurate than the same components loaded at home, and that's been traced to the military pitch seal gluing the bullet in and increasing start pressure. Apparently that can be more consistent than neck tension alone.

If you want to get fancy, RSI sometimes will do a run of their Load Force instruments, which measure to the nearest pound the force used by a press to seat each bullet. If you sort your loads by seating force, it can indeed get you another increment of precision on your target. It's another one of those things that probably won't help if you have a load shooting much over an moa to start with, but which can help make an moa or less get a bit smaller.

[Bart B.]

Unclenick mentions:

As to neck tension, generally speaking, Mr. Guffey has it right: more is better from the starting pressure and ignition standpoint as long as it's consistent. Military match ammo in a number of instances has been found to be more accurate than the same components loaded at home, and that's been traced to the military pitch seal gluing the bullet in and increasing start pressure. Apparently that can be more consistent than neck tension alone.

And military match ammo in a number of instances has been found to be less accurate than the same components loaded at home, and that's been traced to the military match cases not having a pitch seal gluing the bullet in and increasing start pressure but instead using less neck tension. I've broke down 7.62 NATO match ammo to primed case, powder and bullet, then cleaned out the seal, resized the neck, metered the powder back in and seated the bullet. It shot more accurate than the original stuff when fired in the same rifle.

I don't think the pitch (asphaltum) seal makes the bullet release force more consistant than neck tension alone. Note that M118 ammo's inside neck diameter's a thousandth or two larger than bullet diameter from the mouth back to almost the neck-shoulder junction. It's just barely smaller than bulet diameter there. That clearance allows the sealant to be applied all the way around the bullet during assembly.

Both 7.62 NATO M118 (and 30 caliber M72) aresnal match ammo have a bullet release force spec of at least 40 pounds but no tolerance is mentioned. The spec for muzzle velocity spread is 2550 (2640) +/- 30 fps at 26 yards from a 22 (24) inch barrel. And both have 600 yard accuracy specs of 3.5 inch mean radius average; about 10 inches maximum group size. National Match lots were made with select lots of bullets and primers and produced about 2 inch mean radius or 6 inch maximum group size at 600.

Some lots of arsenal match ammo issued to the service teams were noticably worse than others. They had enough muzzle velocity spread that perfect scores on the 600 yard's 12 inch 10-ring were not possible. And things were worse at 1000 yards. 'Twas common for some team members to carry a Lyman 310 nutcracker tool with a seating die adjusted to set those match bullets back about 5 to 7 thousandths of an inch. That broke the seal and got the bullet release force down to around 10 pounds. Tests of some lots having too much vertical shot stringing showed the bullet release force had a 20 pound (or more) spread about 50 or so pounds. Getting that spread under 5 pounds and down where a lesser force was needed to push the bullet out made them shoot much more accurate and hold better elevation.

The best accuracy I know of shooting handloaded or reloaded ammo in shoulder fired rifles happens when neck tension is as low as possible. As long as the bullet's held well enough to survive normal handling in the shooting environment it's used in that's plenty. Which is why most folks shooting long range matches seat bullets with light neck tension; some of those bullets can be pulled out by hand. And they're seated out long so they're set back a few thousandths by the lands. The force needed to push the bullet into the rifling's much more consistant with this method than trying to control it by neck tension alone.

[Bart B.]

hhunter318 comments:

I was actually talking about decreasing neck tension. But from the sound of it it sounds like that is a no-go.

You can easily reduce neck tension using a standard full length sizing die. Get a few 30 caliber expander balls then polish them down to a smaller diameter. 7mm "balls" are typically. .2830" diameter so I suggest making a set starting at .2835" then every .0003" larger up to .2850". Or make one at .2850" then try it for cases with a given neck wall thickness; reducing its diameter as needed. Depending on your cartridge brass hardness, you might have to change these dimensions a bit, but I think you get the idea.

This is exactly whay I did with .308 Win. and 30 caliber magnum full length sizing dies; I have five 30 expander balls ranging from .3080" up in .0003" steps. I'd pick the one needed for different case neck wall thicknesses.

It's a good idea to clean out fired case mouths with a bore brush in an electric drill before sizing them with expander balls; it's easier and you'll get more uniform results.

[frank_1947]

the rule of thumb for benh shooters is .002 to .004 of neck tension this also keeps bullet staraigt, i have tested neck tension with a run out gage it will barely move with out tension and useing a common collet neck die Lee run out was .003 , acceptible but not near as good this was done with 168 gr SMK and Hornady A-max

[hhunter318]

Whew. I learned more in this one thread than I planned on absorbing. I'm going to play with the expander ball idea and if i don't have any luck with that, which I should, heck I'll just buy the dang Redding S-type Bushing die. I'll get to where I'm going at some point. Thanks for all the replies and tips.

hhunter318

[oldmanFCSA]

Note: I did not thoroughly read all of the responses, so apologize if I repeat someone else's posting.

Each and every shot on a piece of brass continually work-hardens the neck and shoulder, changing neck to bullet tension for every loading, which causes you to chase your tail trying to find the answer.

To resolve this, learn to anneal your brass's necks each and every firing to maintain consistency between loadings. Then apply all the other tricks you have learned here to control or change amount of bullet pull force.

Various topics can be found online for annealing, but in my opinion, the best is www.6mmbr.com

Chose your answers wisely - some will tell you I'm all wet - others will have their specialty answers - you do the research, make your own decisions, and learn from them. But in the end, consistency from shot to shot is what counts, whether lots of tension, or little tension, but every loading of cases must be controlled by properly processing each and every time.

The small group record for FCSA of 5-shots under 2" center-to-center at 1000 yards was on brass loaded 47 times, annealed each and every loading. Must be something true about the process.

Read at www.fcsa.org