To turn or not (necks)

[goodgrouper]

How can a bullet jump evenly from the neck of the brass if the expansion of the brass is uneven from a thick and thin side regardless of how it sits in the chamber? The position of the cartridge in the chamber can be horrid in a factory rifle and will no doubt harm accuracy, but that is and additional problem that will only add to an uneven bullet release. It would be hard to distinguish what is causing what so I guess the bottom line is turn the necks to a consistent thickness, and have a good chamber and that will be your best bet for accuracy. /ubbthreads/images/graemlins/wink.gif

 

[Chawlston]

[ QUOTE ]
How can a bullet jump evenly from the neck of the brass if the expansion of the brass is uneven from a thick and thin side regardless of how it sits in the chamber? The position of the cartridge in the chamber can be horrid in a factory rifle and will no doubt harm accuracy, but that is and additional problem that will only add to an uneven bullet release. It would be hard to distinguish what is causing what so I guess the bottom line is turn the necks to a consistent thickness, and have a good chamber and that will be your best bet for accuracy. /ubbthreads/images/graemlins/wink.gif

[/ QUOTE ]

GG,

They just don't get it. Either they have not shot guns that will shoot bugholes or they are not advanced enough in their reloading knowledge to recognize that perfect bore alignemnt is ALWAYS preferred to non-perfect bore alignment.

Maybe a few years from now they will be able to appreciate the fact that .001 off of neck thickness will do more good than harm when trying to shoot tiny little holes.

Come on, if they are trying to prove a theory with factory grade barrels chambered with a variety of reamers that are all nearer to max SAAMI specs over a properly fitting reamer for the brass used, then this is a futile attempt to exchange some knowledge with then and to help someone who genuinely wants to squeeze all the accuracy one can get out of a shooting stick. After all, this is LONGRANGE HUNTING and the techniques used in the quest for game at LONG RANGE. This is not a website specializing on how to achieve MOA accuracy. Heck, if my guns won't shoot under .25moa, I am at the range finding out why.

Almost forgot, partial full-length resizing ensures centering of the case in the chamber and turning the necks ensures the case neck is centered with the body of the case and center of the bore. If folks cannot grasp this, then they should reserve opinion and giving advice on loading technches for long range hunting.

James

 

[foreign]

im not been funny now but i would love for someone to explain how neck turning helps with tension and getting everything loaded for someone with a factory rifle. genuinely want to know, cant get my head around it.

 

[tlk]

+1 on what foreign said. A good discussion on the whys and hows (basics) for a SAAMI chamber (i.e., factory) would do me wonders in getting this concept down fully. I cannot figure out if this activity is a nit or a necessary element in getting to where I want to go with my rifle.

 

[nheninge]

Almost forgot, partial full-length resizing ensures centering of the case in the chamber and turning the necks ensures the case neck is centered with the body of the case and center of the bore.

neck turning does NOT center the bullets/necks. To be truley centered, a case must first have zero neck variance. So... the only way to center a case is to sort by case neck variance (using only cases with zero variance), and then neck turn for uniform neck tension. If a case neck has 2.5 thou variance, then it has a thick side and a thin side and the bullet/neck has to sit closer to the thin side (thus offset from the bore). All the neck turning in the world will not change the fact that the bullet/neck is offset if you start with a case that is offset

 

[woods]

Neck turning for a factory chamber will be most beneficial if you are using a bushing type die, a FL die without the expander, a FL die that has had the neck honed to a certain dimension or a custom made die without an expander. What all those have in common is that the dies size the outside of the neck to a specific circular diameter and any variances in neck thickness are pushed to the inside of the neck. If you neck turn to a consistant neck thickness then there are no variances to push to the inside.

If you use a Lee Collet or a regular die with an expander then neck turning for a factory chamber will not be a "nit".

If you have a custom tight necked chamber then neck turning becomes necessary. Unless you just happen to have brass with the perfect neck thickness to give you the bullet grip you want.

 

[foreign]

so whats the advantage of taking out the expander. i would think if i did this and neck turned that the amount of tension i would have would be heaps.
if i dont neck turn and leave the neck expander in then wont i have all the imperfections on the outside and il have even neck tension,can u explain this for me woods. obviously im a kinesthetic learner.

 

[woods]

Sizing without the expander will improve runout or concentricity. When you pull the expander back through the neck it can and often does create runout. Also if you size without the expander then you do not have to lube the inside of the neck.

When you take the expander out and turn the necks you can take the brass neck thickness down to a specific thickness so that you do not have too much bullet grip. For instance if you have a 30-06 full length die and take the expander out and size the case and the outside of the neck measures .329" and your neck thickness is .014" then the math would be

.329" - .014" -.014" = .301"

that is too much bullet grip of .308" - .301" = .007"

But if you neck turned your brass down to .012" the math would be

.329" - .012" -.012" = .305"

which is about right for a bullet grip of .308" - .305" = .003"

There are ways to minimize the bad effects of the expander but I am no expert in that since I just don't use them.

 

[tlk]

Woods, you are equating the difference in bullet o.d. to case mouth i.d. to a force (bullet grip). Can you give some more info on this? How is .007" too much grip but .003" is just right? How is this quantified and where can I get this data? If I think about this I can see a graph with at least two curves and an intesection point.

 

[nheninge]

I do exactly what woods is proposing for some of my loads. (i.e. neck turning and using standard dies). This works great to control neck tension, and I too shoot for that 0.003 - 0.004 thou neck tension.

The downside is that you wind up working the brass more. Here is what I mean. Every shot fired , the neck expands more (because brass from the neck has been removed) and every time you resize, the die has to size down the neck farther because it expanded farther. This causes additional work hardening of each case every time it is fired and resized and shortens brass life. "No big deal"... IF you anneal the brass every 3-4 firings.

Neck turning is fast and easy and nobody should shy away from it. It is an excellent tool when used properly it WILL help accuracy regardless of the chambering (factory/custom) of your rifle. Neck turning is the only way to ensure uniform neck tension. If a batch of cases has even 0.001 - 0.002 thou difference in neck thickness, then you will have at least 0.001 - 0.002 thou variation in neck tension which has been proven to increase ES and SD at the muzzle!

Here is a link that I think explains it all:

Outside Case Neck Turning for Factory Rifles | The Reloading Press

 

[tlk]

neck turning does NOT center the bullets/necks. To be truley centered, a case must first have zero neck variance. So... the only way to center a case is to sort by case neck variance (using only cases with zero variance), and then neck turn for uniform neck tension. If a case neck has 2.5 thou variance, then it has a thick side and a thin side and the bullet/neck has to sit closer to the thin side (thus offset from the bore). All the neck turning in the world will not change the fact that the bullet/neck is offset if you start with a case that is offset

Nheninge, I don't get something: If I turn the outside of the neck, doesn't that get rid of any thick/thin variation since I am taking off metal from the outside relative to the inside diameter?

After turning, the thickness should be a constant from the inside of the case mouth to the outside of it UNLESS the mouth is thinner in some spots than the cutter is set at. This is the only time the cutter would not correct the variance that I can think of. Is this what you mean by sorting cases based on variance: you are sorting based on case neck walls that are thinner than what you will be turning them down to? And in any event, wont this turning help even those that are that thin since it reduce the amount of variance?

Thanks.

 

[onzah]

My neighbor used to shoot competitive benchrest and tested the theory of whether turning actually made a difference in a rail gun. He shot turned necks and unturned necks and could not tell the difference. He doesn't turn necks anymore.

 

[nheninge]

Here is my attempt to explain...

Not to scale and all numbers are random

Neck turning uniforms the case neck thickness, but not the center of its axis, thus making a case with neck variance "offset from the get go" regardless of turning.

I can guarantee that turning necks does make a difference because it also uniforms neck tension. So unless you want to use a different sizing bushing for every shell or only use cases with exactly the same thickness and no neck variance... neck turning is the way to go.

 

[tlk]

That explains it. Thanks for the illustration.

And leads to my next question: If you f/l size does this negate any of the effects of a case that is variable in thickness?

What I mean is that if the neck is turned we are good there. If the case is f/l sized then the OD is good - any variation is with the I.D. In this case wouldn't the center of the case and the center of the neck be the same?

I am still thinking this one through.