Neck Tension


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ejc
August 1, 2007, 06:23 PM
What is considered the proper dimensional difference between the bullet diameter and the expander ball diameter to achieve optimum neck tension on the bullet.

I ask because a friend is concerned about a ring on the bullet caused by the seating process. I told him that the ring is probably only cosmetic but if it bothered him he could smooth up the edge of the bullet seater or measure the bullet and expander ball to see if there is too large a difference that is causing excessive neck tension and therefore higher pressure to seat the bullet. However, I didn't know what is considered proper for neck tension.

Thanks for your help.

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mc223
August 1, 2007, 06:32 PM
This could vary significantly depending on the caliber, the brass etc. In general terms .003 to .007 is likely to be acceptable. A good chamfer or proper case belling will reduce the occurance of the seater ring. Polishing the I.D. of the seater will help the ring some. Polishing are reducing the size of the expander ball will increase neck tension.

ejc
August 1, 2007, 06:35 PM
I should have said that I am talking about a .223 round.

mc223
August 1, 2007, 08:04 PM
For the 223 I use .005 dif between nominal bullet dia. and sized, VLD chamfered case I.D. I also anneal my cases to maintain uniform neck tension.

USSR
August 1, 2007, 08:14 PM
ejc,

Tell your friend "bushings, and ditch the expander ball".

Don

ejc
August 2, 2007, 10:23 AM
I looked in the Lee reloading manual last night and it recommends a .001in difference between the bullet diameter and the inside diameter of the neck of the case. It states that if the difference is larger, then you are just using the bullet to size the inside of the neck upon seating and wind up with the same neck tension would have been obtained by having a .001in difference in the first place.

USSR, when you say bushing and get rid of the expander ball are you talking about a die that you can get different size bushings for to size the outside of the neck that will control the inside diameter of the case and therefore eliminate the expander ball?

Walkalong
August 2, 2007, 10:34 AM
I looked in the Lee reloading manual last night and it recommends a .001in difference between the bullet diameter and the inside diameter of the neck of the case. It states that if the difference is larger, then you are just using the bullet to size the inside of the neck upon seating and wind up with the same neck tension would have been obtained by having a .001in difference in the first place.
That's bologna (baloney) :) Welcome to THR ejc

USSR
August 2, 2007, 01:14 PM
USSR, when you say bushing and get rid of the expander ball are you talking about a die that you can get different size bushings for to size the outside of the neck that will control the inside diameter of the case and therefore eliminate the expander ball?

Yep, you got it! My brass has never had a nasty expander ball dragging thru my nice, straight necks, pulling them one way or the other. Changing a bushing size for a different make of brass takes all of about 30 seconds.

Don

BsChoy
August 2, 2007, 03:07 PM
Not to hijack the thread but, how do you know what bushing size to use? I have also heard that you should resize them with bushings in 2 or 3 steps in 2 or 3 sizes decreasing a little at a time?? Why?

USSR
August 2, 2007, 04:28 PM
...how do you know what bushing size to use? I have also heard that you should resize them with bushings in 2 or 3 steps in 2 or 3 sizes decreasing a little at a time?? Why?

Take a loaded round that is loaded using the make of brass that you will be using, and then with a micrometer measure the diameter of the neck. If you are loading for a boltgun, I would suggest you subtract .002" from that measurement and order that size bushing; with an autoloader or a rifle that you want alot of neck tension on, subtract .004" from the loaded round measurement and order that size bushing. Example: you have a .308 loaded round that measures .338" at the neck; order a .336" bushing for a boltgun or a .334" for an autoloader. Also, order the TiN coated bushing so you don't have to lube your necks. The reason Redding suggests you go in steps is, if you have a large neck diameter on a fired round and then try to reduce it more than say .005" (say from .342" to .334"), the bushing will reduce the case neck to a diameter smaller than the bushing size. In this case, order a .334" bushing AND a .338" bushing, and reduce the case neck to .338" PRIOR to reducing it to .334". Hope that helps.

Don

BsChoy
August 2, 2007, 05:15 PM
Outstanding, thank you Don.

OKIE2
August 16, 2007, 08:30 PM
This will blow your bushing therory all to hell. .004 smaller bushing will not give you any more neck tension then the .002 under size bushing.

look at this all I did was removed the expander in my 308 die this is what I got for neck tension
.001

Useing Federal 308 brass
I did 2 cases both ended up same dims in each step.
Here is what I got.
NECK SIZES
fired case neck .345
sized w/0 expander .330 down .015
bullet seated .340 up .010
bullet pulled out .339 down .001
bullet no different than new after pulling.
This gives me a .016 brass thickness in neck area.

USSR
August 16, 2007, 09:30 PM
This will blow your bushing therory all to hell. .004 smaller bushing will not give you any more neck tension then the .002 under size bushing.

look at this all I did was removed the expander in my 308 die this is what I got for neck tension
.001

Useing Federal 308 brass
I did 2 cases both ended up same dims in each step.
Here is what I got.
NECK SIZES
fired case neck .345
sized w/0 expander .330 down .015
bullet seated .340 up .010
bullet pulled out .339 down .001
bullet no different than new after pulling.
This gives me a .016 brass thickness in neck area.

OKIE2,

Taking the expander ball out of a regular set of dies is not the way to go. All you are doing is SERIOUSLY overworking and work hardening your brass! Also, the outside dimension of brass after you have pulled a bullet does not indicate the amount of neck tension on a bullet when it is loading in the neck.

Don

Clark
August 17, 2007, 12:24 AM
The .223 neck will spring back .001" from elastic deformation. [45acp can spring back .002"]
Any more is plastic deformation.

Getting just .001" less inside diameter than the .224" bullet is not easy, becuase of variations in neck thickness and dies.

A .246" Redding "S" bushing is like a .245" Forster factory honed die.

But do the best you can to get close.

OKIE2
August 17, 2007, 01:59 PM
Don
I am not working my brass any more than the die does with the expander
in it. But I do admit the necks should not be worked that much. I am going to check all my 15 other dies I load with to see if they do the same thing if so
I will get them reamed out a little bigger.
And how much tension do you think I have on the .308 then if not .001?
Bob

koja48
August 17, 2007, 04:20 PM
My 223 handloads for a variety of ARs are at 0.005 using Redding dies, and they shoot just fine. Haven't tried bushings yet, but may someday.

Walkalong
August 17, 2007, 05:46 PM
To make matters worse the amount of "springback" of brass changes through its life as it work hardens or is annealed etc. etc.

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