Neck tension .001 or .003.

bakerboy

bakerboy

New member
Which is the correct neck tension, .001 or .003? Or are both numbers correct. Redding says .001. Various gas gun authors say .003 and even .004 on moly bullets (D. Tubb). So I'm thinking .001 is the minimum, and is ok for bolt guns while more tension, .003, is required for autoloaders.
What's everybody using?


For the uninitiated: Neck tension is defined as the difference in diameter, measured at the neck between a loaded and empty case. The empty case being smaller creates tension when a bullet is seated.
 
You know something.. I never have measured it. I use my resizing die.. and then trim it.. clean the primer pocket and debur the flash hole.. run a brush thru the neck and bevel the neck.. etc etc.. prime it, put the powder in.. and seat the bullet. What caliber are you loading for?
 
Neck tension is better measured by how many pounds it takes to move the bullet in the case. This varies a lot with different brass.

Jack
 
Quote:
For the uninitiated: Neck tension is defined as the difference in diameter, measured at the neck between a loaded and empty case. The empty case being smaller creates tension when a bullet is seated.



The "tension" is the force or squeeze on the bullet by the neck, not the amount of undersize.

It will vary by the hardness of the brass, the thickness of the neck walls, and the depth the bullet is seated.

If adjusted to 0.001" undersize, bullets might fall out of the case if they are in a case that has been turned to a wall thickness of 0.008", and is soft brass, and the bullet seating depth is 0.10"

On the other hand, the same undersize will hold a bullet rock hard if the walls are 0.015", the brass is hard, and the bullet is seated 0.30".

Jack's comment is the best way to judge - the force to seat it is proportional to the force of the neck grasp.

CatShooter.
 
I'll accept both of the above explanations on tension.
However, what reloader has the ability to actually measure the poundage to move a seated bullet? Answer: None. And, trying to shove a bullet further into the case by hand only
indicates lack of tension, and not excessive tension. So it would seem to me that measuring the "relative" tension as defined in the original post is a measure that will produce a more consistent product.
 
With the bushing type dies today using either Wilson or Redding bushing you can adjust neck tension that way. If you use an arbor type press you develope a pretty good feel for seating bullets. Sinclair makes bushing in 1/2 sizes for the 6ppc and I think Custom Products does also. Using some bushing type dies you only size down 1/2 the neck. On my deer and elk rifles I prefer alittle more neck tension since these rds will be handle pretty hard and that may be the case with gas gun magazines and recoil.
Bushing size depends alot on if you clean up the necks or not. I shot moly bullets when the first came out and could see them using alittle more neck tension. I use to do the ft lbs on my BR rifles so developed that feel and just use that on my varmit rifles and I keep a fair amount of different size bushing on hand.
 
I use anywhere from .001"-.002" for any rifle I plan on using for accuracy work. .003-.004" would be for a hunting rifle that I carried around and inserted and removed rounds from often.

measure the sized dia of a case NK, then the dia after seating the pill, the difference is the neck tension in .001"s.

as the brass becomes work hardened, the tension will "appear" to stay the same (according to the mic), but groups will open up as the brass loses it's elasticity and will not hold the same pressure on the bearing surface of the bullet. This is when brass must be annealed to get it's elasticity back to restore the nk tension you started your load work with. The bushing dies allow you to chase the failing nk tension by inserting smaller bushings until your group tightens back up. This only last for a short time and nks will crack or split. /ubbthreads/images/graemlins/smiliesmack.gif Annealing to restore elasticity is the way to keep groups tight and ES as well as SD low. /ubbthreads/images/graemlins/grinning-smiley-003.gif

any way you want to measure it, the tension is DIRECTLY dependant on the elasticity of the brass.
 
It's real easy to measure neck tension, all you really need is a bathroom scale. Put a piece of wood on the scale stand a round on it and push on the bullet with a small piece of 2X4. Watch what the scale reads when the bullet starts to move. It is even easier if you use a drill press to apply pressure. The neck tension for an AR should be between 50 and 100 pounds.

Jack
 
Quote:
It's real easy to measure neck tension, all you really need is a bathroom scale. Put a piece of wood on the scale stand a round on it and push on the bullet with a small piece of 2X4. Watch what the scale reads when the bullet starts to move. It is even easier if you use a drill press to apply pressure. The neck tension for an AR should be between 50 and 100 pounds.

Jack

Thats how I learned bathroom scale, 15/20lbs is about right for a small caliber and you can do that much by hand.
 
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