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Neck Tension

What are the effects of neck tension,does it help make a load more accurate or are there other effects as well.
I have three different dies for 308 and the all give a different neck tension and would like to use one that helps the load the most for target shooting.

Thanks
 
Neck tension certainly does affect accuracy, similar perhaps to the influence bullet seating has on accuracy; perhaps long range stability would be a better term than accuracy. When neck tension is inconsistent the muzzle velocity will also be inconsistent. But the influence of neck tension on accuracy is not, IMO, as dramatic as some would suggest. I give greater weight to concentricity than neck tension. Nevertheless, at my reloading bench, the least amount of neck tension that is reasonably attainable and equalizing neck tension from one round to the next is the goal.
 
Lapua40x
For the most part do you try to have the least amount of neck tension so the release of the bullet will have the smallest varriance??
Is .003 to much grip on the bullet to help with ES or if no mater the tension as long as they are uniform from neck to neck can you control ES.
 
bench said:
Lapua40x
For the most part do you try to have the least amount of neck tension so the release of the bullet will have the smallest variance??
Is .003 to much grip on the bullet to help with ES or if no mater the tension as long as they are uniform from neck to neck can you control ES.

I like neck tension at > .001 and <.002. However, if all I could get was .003 and a concentric well centered and consistently seated bullet I'd probably work with that until I could turn the necks and open them up a bit. Some of my restraints involve lack of funds to acquire all the fancy sizing equipment I'd like to have (I do have friends from whom I can borrow it but try to avoid doing that) so I sometimes have to practice with the best product I can develop until the bucks in the bank grow up.
 
LOL, OH THE MONEY ISSUE And I thought this would be a fun sport now I need a second JOB.
Thanks for the help
 
There is a lot of work and expense that goes into achieving the exact same neck tension on each round. For the most part this is something the advance re-loader does when building competition ammo. You have to start with good brass. The neck thickness needs to be the same all the way around. If not, you need to turn the neck. You will need several bushing sizes to handle different neck thicknesses and the small variances in bullet diameter from brand to brand. Some bullets like more tension than others. Some use almost no tension when jamming the bullets. I like more with my non-crimped AR bullets. I don't know if this is still the norm but some of the point blank shooters never resized at all. They just primed, charged and inserted the bullet a little long by hand. When they close the bolt the bullet is just touching the lands. If you want to shoot 6" 1000 yard groups you will need to do this. Later! Frank
 
The cheapest way to attain the neck tension you desire is call lee reloading and have them make a collet die which is cheap and when you try the die and figure out what the tension will be,they will make you custom mandrels to get exactly the .002 you desire.Look up the collet die and read about it.It is about 20.00. Maybe someone here will chime in and explain it better than myself.
 
Lee and forster have suspended custom work. Lee is supposed to resume in the spring. >:( Was looking forward to trying a custom collet die for my Shehane.
 
Neck tension is the amount of total pressure holding a given amount of surface area. In my dasher I only neck size .075 length. My size bushing may be smaller but total neck tension will be less. Good shooting Larry
 
bench said:
What are the effects of neck tension,does it help make a load more accurate or are there other effects as well.
I have three different dies for 308 and the all give a different neck tension and would like to use one that helps the load the most for target shooting....

As an aside, you might also want to consider which of the 3 dies best matches your chamber? Regards JCS
 
bench said:
LOL, OH THE MONEY ISSUE And I thought this would be a fun sport now I need a second JOB.
Thanks for the help

It may seem expensive but as hobbies go, it's less expensive than some. Hot Rodding? The hobby of my youth is now so expensive that I can buy half a dozen "Super Custom" rifles for the price of one "Hot Rod".

What's really nice about my shooting hobby is that I can "go as fast as I want" without getting a ticket 8)

Second job? Not me, I've just decided to spend my kid's inheritance ;D ;D
 
Amlevin,now that is really funny.I am doing the same theing.LOL
 
bench said:
What are the effects of neck tension,does it help make a load more accurate or are there other effects as well.
I have three different dies for 308 and the all give a different neck tension and would like to use one that helps the load the most for target shooting.

Too much or too little neck tension will if course affect consistency of propellant ignition and the resultant variation in pressure curve of each round fired. We go to some trouble to ensure neck tension is 'tuned' to give us the consistency we feel shows results on paper.

Three 'factory' dies probably have small differences in case dimensions as well as the neck portion, to make no mention of the expander they come with.

Do you use an expander? First thing I do with a new (bushing!) die is pull it off & toss it into a box....
 
If you can use a standard LEE neck sizing die with your caliber, you can increase the bullet grip by "polishing" the mandrel in the area of the collet. You can buy extra mandrels for not much money and make a bunch with different end neck diameters.

Of course, you can do this same trick with a custom LEE die, as I do with my 6BRX. Right now I get 0.00075" consistently for long range BR. By consistent I mean an SD of 0.00026" on the sized case diam.
 
If you can use a standard LEE neck sizing die with your caliber, you can increase the bullet grip by "polishing" the mandrel in the area of the collet.
[/quote] Maybe I'm missing something here. If you polish the mandrel only in the area of the collet the neck diameter reverts to the pre-polished diameter as the case is pulled out of the die. The mandrel needs to be a uniform diameter from neck to de-capping pin. Yes?
 
When I see posts with measurements down to the hundred-thousandths my eyes glaze over.

That is the BS you just read that caused that. Later! Frank
 
LHSMITH said:
When I see posts with measurements down to the hundred-thousandths my eyes glaze over.

Last time I saw those tolerances we were doing work for NASA using equipment I could never afford.
 
gotcha--The dia you want has to be at the top where the collet squeezes the neck, any thing under that to the decapping pin can be smaller as long as you are not using the portion for expanding of some sort w/o the collet.
 
normmatzen said:
If you can use a standard LEE neck sizing die with your caliber, you can increase the bullet grip by "polishing" the mandrel in the area of the collet. You can buy extra mandrels for not much money and make a bunch with different end neck diameters.

Of course, you can do this same trick with a custom LEE die, as I do with my 6BRX. Right now I get 0.00075" consistently for long range BR. By consistent I mean an SD of 0.00026" on the sized case diam.
I can get the same degree of accuracy/precision, but at least to me, this sounds better than it actually is.

The reason is say for example in my last prep of twenty eight 223 cases, I calculated case neck internal diameter (ID) by taking the neck outside diameter (OD) of each case and minus two neck thickness from the same case. The OD of these cases had a range of 0.00082" (SDEV of 0.00021”) and the necks thickness even better at 0.00015" (SDEV of 0.00003”). The resultant neck hold was calculated by taking the number 0.223” and minus out the ID - the average neck hold was 0.00167" but the variance was 0.00072” (SDEV of 0.00023”) most of which as expected was due to the variance in OD and not neck thickness.

The bottom line is a variance of 0.00072” out of an average neck hold of 0.00167” means that there was a 43% variance in the neck hold! The lesson for me here is since the hold is so minute, even a very small variance in ID/OD makes a huge difference. AND remember we are not even taking into account the variance in bullet diameter.

So why such a high variance in ID/OD? All the cases were sized with a Lee Collet die which has a neck thickness variance of 0.0002” (SDEV of 0.00007” out of 10 measurements) so it is not the die. My suspicion is that it is caused by a variance in spring back. Now all of these cases have already been properly annealed with a BenchSource and so….. ::)

Would be very interested in hearing what the experts think of this. :-\
 

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