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proper amount of neck tension

 
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  #8  
Old 09-02-2013, 02:35 PM
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Re: proper amount of neck tension

Good way to clarify Broz. But there is still more to it.
Some see your annealing adjustment as regaining tension, when it's actually reducing springback. And while your adjustment regains the desired interference fit, tension out of this is still reduced.

Your annealing adjustment falls apart on expansion, and you will expand, even if it's done with bullet seating only. That's when reduced springback from annealing leaves less tension than using a bushing adjustment.
The REAL problem adjusted for here can be better addressed directly: Stop changing springback(another thread).

It's important for folks to know that the only thing gripping a bullet is springback, and there are limits to this.
Your set interference fit only needs to include the neck's springback, because that's all the grip you're going to get anyway. More down sizing is just overworking neck brass(changing springback, leading to adjustment/tail chasing).

Try this;
Size necks varying amounts leaving >3thou under cal as measured, seat bullets & again measure neck diameters, then pull them, and measure the springback from seated neck diameters. It's always gonna be 1-3thou, and this is all that ever grips a bullet.
If you anneal one of these necks and do the same test, you'll see less springback from it than non-annealed necks.

jfseaman, your 4thou interference fit does not represent 4thou of tension. If you sized your necks down 10thou under cal, it would not mean you have 10thou of tension. It only means 10thou interference fit for bullet seating, which would cause very high bullet seating forces(because you're using your bullets as an expander), but no more tension at all.
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  #9  
Old 09-02-2013, 02:48 PM
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Re: proper amount of neck tension

Agreed Mike. But the problem I want to deal with is the fact that not all brass hardens at the same rate. Thus why some of the bullets had tension some did not, before annealing. So I anneal in a effort to keep the brass equal in spring back case to case.

In the end there is more than one way to skin the cat. One can beat any method to death. But what I have done is developed a method that has shown me results worth repeating my ELR groups. I have kept track in the log book for a long time to get multiple data samples. I am confident in saying this method works well for me in the type of shooting I do.

YMMV

Thanks
Jeff
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  #10  
Old 09-02-2013, 03:06 PM
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Re: proper amount of neck tension

Quote:
Originally Posted by Mikecr View Post
...jfseaman, your 4thou interference fit does not represent 4thou of tension. If you sized your necks down 10thou under cal, it would not mean you have 10thou of tension. It only means 10thou interference fit for bullet seating, which would cause very high bullet seating forces(because you're using your bullets as an expander), but no more tension at all.
OK. Not well just now, flu. But I'll do all the normal 'prep', seat a bullet, pull it then remeasure ID.
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  #11  
Old 09-02-2013, 07:24 PM
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Re: proper amount of neck tension

Was feeling better this afternoon so went to the shop. 30-30 was in the reload queue so went with that. Checked the 308, 300WSM and 300RUM that were part way through but up to at least the sizing point and all ID were the same.

Measured with a dial micrometer not digital.

Sized case:
ID .304
OD .324, the FC 30-30 case had a measured thickness of .010. I have 3 tools for this including a laboratory grade tubing tester.

Seated bullet
OD .326

After bullet pulled:
ID .305
OD .325

Resized case
ID .304
OD .324

Bullet diameter before and after was .308.

So...

Per Mikecr that is a .002 neck tension.
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  #12  
Old 09-03-2013, 05:27 PM
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Re: proper amount of neck tension

Close, but,,
Your carefully measured neck thickness of .010 wrapped around a bullet measuring .308 = .328 loaded neck OD (not .326).
If it sprang back to .325 after pulling the bullet, that's .003" of tension.

No combination of your reported measure results in .002 neck tension.
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  #13  
Old 09-04-2013, 10:23 AM
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Re: proper amount of neck tension

Quote:
Originally Posted by Mikecr View Post
Close, but,,
Your carefully measured neck thickness of .010 wrapped around a bullet measuring .308 = .328 loaded neck OD (not .326).
If it sprang back to .325 after pulling the bullet, that's .003" of tension.

No combination of your reported measure results in .002 neck tension.
Now I understand 'neck tension' but wow Mikecr

from my point of view your style of communications is insulting and incendiary.

How old are you?
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  #14  
Old 09-04-2013, 07:19 PM
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Re: proper amount of neck tension

You've challenged my communications several times now(several threads), and with little more than generalizations, errors, and insults.
But we're getting along just fine. I am glad you understand neck tension.
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