Neck Tension Variables

rodell · Jun 15, 2016

In my quest for the ever smaller group that I don't need for anything I actually shoot, I've become obsessed with neck tension (and concentricity, but that's for another post).

One thing that I'm playing with is "clean" cases that have been resized and wet tumbled to shiny goodness vs, once-fired that are sized and tumbled in dry media.

I definitely notice the difference when seating - the clean brass definitely takes a little more effort to seat.

Does anyone have any pull test data that might help me understand how much this particular variable changes the grip on the bullet? I've been trying to figure out how to measure it - possibly a force gauge on an anvil press and push the bullet into the case (no powder).

I realize it may not matter as long as I'm consistent, but I just have to know!

Thoughts?

Darkhorse · Jun 17, 2016

A tool like that would be nice, but since I don't have access to one I depend on feel. After
45 years of handloading my feel is pretty well calibrated.
I address this a couple of ways, during initial fired, dirty case prep and post prep on basically the same cases.
First I have a simple mandrel I chuck up in my table drill press. This mandrel holds steel wool. I turn on the drill and run all the case necks up into the mandrel until the excess
carbon is removed.
Next all the case necks are annealed.
When I lube the cases I put a trace of lube on a brush and lube the inside of the case necks. Then all cases are sized, then neck turned to approx. 85% clean up, then dechamfered inside and out.
When the bullet is seated I expect the feel to be same on all cases as they are now as identical as I can make them.
After a couple of loadings I might find some seat with more pressure than the rest. These I anneal again and possibly steel wool the case necks again if the case appears to be in a condition to fire safely.

rodell · Jun 17, 2016

I have a stupid hangup about clean brass, so as long as I clean it the same way each time, and use the same size sequence I will have the consistency I want.

I am going to figure out some way to measure the difference between the squeaky clean case and the fired case (both sized).

30-338 · Jun 18, 2016

rodell":23molxbr said:
In my quest for the ever smaller group that I don't need for anything I actually shoot, I've become obsessed with neck tension (and concentricity, but that's for another post).

One thing that I'm playing with is "clean" cases that have been resized and wet tumbled to shiny goodness vs, once-fired that are sized and tumbled in dry media.

I definitely notice the difference when seating - the clean brass definitely takes a little more effort to seat.

Does anyone have any pull test data that might help me understand how much this particular variable changes the grip on the bullet? I've been trying to figure out how to measure it - possibly a force gauge on an anvil press and push the bullet into the case (no powder).

I realize it may not matter as long as I'm consistent, but I just have to know!

Thoughts?

If you used arbor die for seating you could get K&M press.

http://kmshooting.com/arbor-press.html

Wyo7200 · Jun 18, 2016

I kind of had the same question in this thread: http://forum.nosler.com/viewtopic.php?f=4&t=33456

This is the article that I thought was from 6mmbr talking about the effects of sonic cleaning-
http://bulletin.accurateshooter.com...eaning-case-neck-friction-and-bullet-seating/

I think that there is some truth to a lubed case being more consistent down range on paper.

Darkhorse · Jun 18, 2016

I no longer clean my cases with a tumbler. Now I do it the hard way and clean one at a time with Brasso and cloth. I'm retired with plenty of time. So my cleaning doesn't affect my neck tension.
When I run the steel wool through the case necks this is all the cleaning the case neck gets. This operation removes all or most of the carbon buildup.
When I lube the case mouth it is only for resizing, though residual lube remains and this helps contribute to neck tension.
I find it does not make much different between wet lube and dry mica.

ElmerThud · Jun 28, 2016

I can't help with any pull test data, but I have time when I reload, so I reload all my ammunition, but only in 'small lots' for zero/hunting, however, I do chase small groups.

Before I resize, I ensure the case is clean & inside of the case neck has been brushed with a bronze brush & the carbon removed.
I have no idea what this does for neck tension, but it certainly helps with resizing and bullet seating.

Once I'm happy that my F/L resizing die is set to achieve both concentricity and bumps the case shoulders to my fireformed headspace dimension, I resize a small batch.

When the round is is charged and finished off, my final stage is to crimp using a Lee factory crimp die. This I'm sure evens out neck tension variables and my chrono certainly provides evidence of close ES.
In itself, that narrow ES is proof that pressures are quite even round to round.

The result is usually .25" MOA @ 100 yds. Consistently. That's hand holding with arm on a rest & not using a bipod or indeed any other rest other than my arm/elbow on the bench.
As you can see from last w/ends target, I still can 'pull' a shot, but mostly, I don't.
Cheers, ET

DrMike · Jun 28, 2016

Very gratifying riflery, ET; very gratifying, indeed.

ElmerThud · Jun 28, 2016

DrMike":rjjuqwth said:
Very gratifying riflery, ET; very gratifying, indeed.

Many thanks DrMike. It was posted only to illustrate what can be achieved with help from folk on this site, some attention to set up & use of available reloading tools. It's worth the effort.