What is the purpose of neck tension?

[Dthomas3523]

In theory, neck “tension” only matters as long as it’s consistent. When the release is not consistent, your velocity numbers will be more variable.

What happens when most people say they found that “my rifle likes .003 neck tension”……what has really happened is the process they used to get that .003 interference fit gave the most consistent release. And it’s a two part deal. The initial release dictates pressure and thusly velocity and also dictates if the bullet shifts enough to one side (say the case neck isn’t uniform in one or more of the various possibilities) then it will show up on paper.

Like most things, most loaders don’t actually understand what’s happening. They just assign a value that works for them. Which is perfectly fine as long as they don’t go around trying to educate people beyond “I did this and it worked.”

 

[308pirate]

You guys are good.
So I've posted this because I'm fishing for the general mindset of what tension does as I'm in the process of making another video on the subject.

Here's a scenario: Two test groups, same charge, same brass, same development. Everything is the "same" as you can get it.
One group seated at .003" tension or 45# press weight one has zero tension set into the case mouth by hand.
Now what happens since neck tension is the all deciding factor??

Instead of some bullshit trolling post, why don't you just conduct your experiment, post the results AND methodology, and let your data speak (or not) for itself.

If you know what you're doing you won't mind the scrutiny

 

[Gungnir388]

Neck tension provides an applied force upon the bearing surface of the bullet, I think we are calling it interface now?! Is not the more important question how the interface affects other parameters?
Combustion + pressure + bullet release = velocities & the consistency of it all

Also it holds the bullet

 

[SicVic]

Instead of some bullshit trolling post, why don't you just conduct your experiment, post the results AND methodology, and let your data speak (or not) for itself.

If you know what you're doing you won't mind the scrutiny

Mr Pirate,
Trolling; yes trolling for information so I'm informed regarding the subject.
This in turn helps me to cater the information so that someone who has questions can watch the video and understand the certain subject a little better. Visual learning I guess.

So now that I've tried to answer your question I have one for you.
Does neck tension increase pressure/velocity? If so at what point and is it directly related?
Thanks for commenting.

 

[357Max]

I view neck tension as 1 part of a system that I don't have a full grasp on yet. It's importance & ideal tolerance range is like any system, application dependent.


How much does it really matter?? Doubt it's worth a second thought for a lever 30-30 hunter or a range blaster. Std cheap dies + compitent reloading methods will be plenty good.

I do think it's worth some thought if application requires low SD/ES. Correctly understanding what is needed (I don't) could cut a lot of rounds off load development.

My novice attempt to list variables affecting tension requirements least to greatest. Not numbered cause the order of importance will probably never be in agreement. Any given system will be some combination of the below items.

• Bench rest with bullets seated to lands
• Faster end of powder for given round
• Minimal jump
• Bullet jumping significantly
• Long case neck length
• Short case neck length
• Overbore case
• Under-bore case
• Under filled case
• Compressed load
• Slow powder
• low powder capacity
• High powder capacity
• Gun weight-recoil impulse ratio
• Mag fed
• Tube mag fed
• Auto loader

I think tension is the appropriate term since interference/press fit does not equate to bullet grip. Hence the seating pressure guage setups.

Stuff affecting final tension.

• Interference fit of brass
• Brass neck length
• Bullet bearing surface engaged with neck
• Brass type
• Anneal of brass
• Neck lube

Supposedly affects final tension

• Time elapsed since bullet was seated
• Moon phase
• Aliens
• Bigfoot

Don't know the answer as to how to best tune tension. I'm near the bottom of a steep learning curve.

Something I've stated paying attention to is the carbon on the outside of my fired cases.

For example:

I got a good load worked out in my 6GT.
I always put the rounds back in the case in the same order they were loaded.
When looking at the fired cases from 3 different projectiles, each loaded 3 different lengths, but all same powder charge. I noticed a bit of a pattern. The 2 best loads had the carbon on the outside of the neck stop about .050 above the neck shoulder junction. It was a defined ring showing the neck fully sealed to the chamber. I'm using Vit 555 with a slightly compressed load & .0027 jump. This powder is on the slower end of the spectrum for the 6 GT. I have not tested, but suspect if I backed off the neck tension (currently .002) SD/ES might go up.

That was a long fucking way of saying that I think there is a minimum required tension for my load to get the neck well sealed given a slower pressure curve. If I start seeing carbon tracking down the shoulder I will add seating tension or switch to a faster powder. Could be wrong, but that's my current train of thought.

 

[308pirate]

Does neck tension increase pressure/velocity? If so at what point and is it directly related?

In theory yes.

In practice I don't care. I don't care AT ALL about the reloading minutia that some waste tons of time and ammo on.

 

[SicVic]

357,
Once you noted that Bigfoot has an effect on tension I knew that I was listening to a person with a wealth of knowledge on the subject.
Great write up as the entire subject does seem to be as elusive as the Squatch himself.
I'm in complete agreement with your tension statement.
You can have zero measured tension from a caliper but still have the bullet not fall into the case mouth freely.

By eliminating the tension as much as possible I seeing that the system sort of self corrects for the errors that we induce.
If you seat at 3# pressure vice 30 the differential range will be much closer.
If you soft seat into the lands you bypass the entire need to find max oal which can be a whole other Circus on its own.
Soft seating is not practical at all but it removes the complications of issues related to neck tension.
I wanted to bring it to light not because it's something new but to showcase that there are other avenues rather than someone telling a new reloader that .002" is what you have to do and if you don't your stupid.
Thank you for your post...
(The carbon ring) lol. I can tell this one is sealing and combustion is happening more evenly... Another Rabbit hole!

 

[OXN]

Like most things, most loaders don’t actually understand what’s happening. They just assign a value that works for them. Which is perfectly fine as long as they don’t go around trying to educate people beyond “I did this and it worked.”

Reloading is definitely all about that Dunning Kruger effect life. About two years into it so far and realizing there are so many variables at play that most of the assumptions people make about load development are either not repeatable or due to something completely different than what they think. Great info in this thread!

 

[918v]

Reloading is definitely all about that Dunning Kruger effect life. About two years into it so far and realizing there are so many variables at play that most of the assumptions people make about load development are either not repeatable or due to something completely different than what they think. Great info in this thread!

Specifically what assumptions are those?

 

[Jscb1b]

357,
Once you noted that Bigfoot has an effect on tension I knew that I was listening to a person with a wealth of knowledge on the subject.
Great write up as the entire subject does seem to be as elusive as the Squatch himself.
I'm in complete agreement with your tension statement.
You can have zero measured tension from a caliper but still have the bullet not fall into the case mouth freely.

By eliminating the tension as much as possible I seeing that the system sort of self corrects for the errors that we induce.
If you seat at 3# pressure vice 30 the differential range will be much closer.
If you soft seat into the lands you bypass the entire need to find max oal which can be a whole other Circus on its own.
Soft seating is not practical at all but it removes the complications of issues related to neck tension.
I wanted to bring it to light not because it's something new but to showcase that there are other avenues rather than someone telling a new reloader that .002" is what you have to do and if you don't your stupid.
Thank you for your post...
(The carbon ring) lol. I can tell this one is sealing and combustion is happening more evenly... Another Rabbit hole!

As I understand it, minimal to no carbon is best as this is a sign of the neck sealing. Right?

 

[Wheres-Waldo]

Default Reloading Forum Response.

A.) Needs bigger sample size, results invalid.
B.) Improper testing procedures, results invalid.
C.) Unpopular opinion/not in style, results
invalid.
D.) I disagree and deem your sources insufficient, results invalid.