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# How do you control neck tension?

#1
05-25-2010, 10:49 PM
 Silver Member Join Date: Dec 2008 Location: SW Idaho Posts: 193
How do you control neck tension?

How do you control neck tension under a variety of sizing methods?

It makes sense to me that when using a full length die with expander ball (RCBS), that neck tension should be consistent. However, using this setup how do you reduce neck tension?

I've read that you can get good results by using FL sizing w/o the expander ball. With that method, how do you control neck tension? If you bump the shoulder back by a couple thou or so, does that tighten the neck tension...and is that how you control it?

How about neck sizing? Same as above?
#2
05-25-2010, 11:44 PM
 Gold Member Join Date: Jun 2006 Location: Shangri-La Posts: 903
Re: How do you control neck tension?

The way you control neck tension or bullet grip by sizing without the expander ball is to outside turn your neck thickness. For example, if you are sizing for a 30-06 and:

Your sizing die sizes the neck down to .330"
You want .002" bullet grip

then the math would be

caliber - bullet grip = desired ID of neck .......... .308" - .002" = .306"
die dimension - desired ID of neck = total brass thickness ........... .330" - .306" = .024"
total brass thickness / 2 = thickness each side ............. .024" / 2 = .012"

So if you outside neck turned your brass to .012" then you could size your brass without the expander ball and have .002" bullet grip .............. theoretically

I say theoretically because there are some other variables that will have some effect, namely springback which is a function of the softness or work hardening of your brass neck and how accurately you can outside neck turn to an exact .012".

If you really want to get exact then it helps to have an accurate way to gauge the ID of the neck. I use pin gauges

they measure to the .001" but you can tell additional information by how easily or difficult the pin gauge goes in.

IMO bullet grip is also affected by the condition of the inside of your neck. IOW any scratches, burrs, left over lube etc. will also affect bullet release and seating depth variances. To solve this problem I use scotchbrite and mica

I recently did a test where I size with 3 methods on 5 case each and gauged the resulting bullet grip.

Regular sizing die with expander ball
Bushing style Redding neck sizer
Lee Collet Neck Sizer

Using the pin gauges and to the best of my abilities, I came up with the following conclusions

The Lee Collet had the exact same ID throughout the 5 cases. IOW the same pin gauge went in with the exact same resistance.

The expander ball did almost as well using the same pin gauge but with varying resistance.

The bushing neck sizer varied between three pins with it tight on one side and loose on the other side of the center pin size. These case necks were outside neck turned to the best of my ability.

Lots of ways to skin this cat but doing it this way my velocity extreme spreads have mostly dropped to the single digits and my groups have shrunk at the longer distances.

YMMV
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#3
05-26-2010, 05:39 AM
 Gold Member Join Date: Dec 2001 Posts: 787
Re: How do you control neck tension?

Quote:
 Originally Posted by bookworm How do you control neck tension under a variety of sizing methods? It makes sense to me that when using a full length die with expander ball (RCBS), that neck tension should be consistent. However, using this setup how do you reduce neck tension? I've read that you can get good results by using FL sizing w/o the expander ball. With that method, how do you control neck tension? If you bump the shoulder back by a couple thou or so, does that tighten the neck tension...and is that how you control it? How about neck sizing? Same as above?

Myself I use bushing dies and if you get the redding type S dies you get a standard type expander also what called a Pin Retainer that allows bushing to set neck tension.
#4
05-26-2010, 08:18 AM
 Platinum Member Join Date: Oct 2007 Location: Mountians of SW NC, near Asheville Posts: 1,584
Re: How do you control neck tension?

The meaning of the first two posts is that you can't control it with standard dies, there is no such adjustment.

Use Lee Collet neck dies, they will take care of all the variables as well as it can be done and without any fuss.

If you wish to do a shoulder bump, get a body die OR bore out the neck of a FL die a few thou over max so it won't make neck contact.

There is no benefit in more than 1 to 1.5 thou of "bullet tension" (an interferrence fit actually), any more will only increase run-out.
#5
05-26-2010, 11:29 AM
 Platinum Member Join Date: Aug 2003 Location: NC, oceanfront Posts: 2,979
Re: How do you control neck tension?

I use bushing neck dies(Wilson or JLC).
My 'tension'(or as mentioned 'interference') is set at .001" after springback.
For 'grip amount on bearing', which is a release force variance, I adjust via partial sizing.
I've chosen a convenient starting standard here as 1cal, and it's turned out very well. That is, I neck size to ~.22" down the neck from it's mouth for 22cal bullets, .26" for 26cal bullets.
I can adjust this easily with these dies(for load development) one way or another.

After sizing a batch of necks, I run each through a seating force gauge of mandrel design to verify all will actually seat with the same force(a force chosen during load development). For any that don't, I set aside to stress relieve in another batch.

It doesn't make sense to size the entire necks, just because it can be done. Especially when bullet bearing doesn't even reach so deep! Such action is not only bad for brass life, it likely reduces performance potential from a load.
#6
05-26-2010, 12:24 PM
 Platinum Member Join Date: Nov 2005 Location: Texas Posts: 1,844
Re: How do you control neck tension?

I have my dies made (bushing type) when the rifle is made. Good stuff above but do not forget--------Never Mix brass that has been fired 5 times let’s say with brass that has been once fired. The more brass is worked without being annealed the less “spring back” consistency there is which translates to inconsistent neck tensions if you are mixing brass.

Also when going to shoot a 1K event I will always load the night before to ensure a "fresh" set in the case. A trick I learned from Speedy Gonzalez and Rich Machholz at Sierra who I shoot with.
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Last edited by Boss Hoss; 05-26-2010 at 06:52 PM..
#7
05-26-2010, 05:09 PM
 Platinum Member Join Date: Aug 2003 Location: NC, oceanfront Posts: 2,979
Re: How do you control neck tension?

Boss, I hope you didin't get 'less annealing = less springback' from them..
If so, they've sent you snipe hunting!

Annealing doesn't restore tension, it relieves excess.
Well, technically 'annealing' ruins brass. It's 'stress relieving' that we do.

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