What is the purpose of neck tension?

[SicVic]

So I have my opinion and I load accordingly.
I talking about a bolt gun ( mine is 6.5 CM)
Please don't write a novel or attach a bunch of tutorial links; just a few quick highlights will do.
If you think it does 3 jobs then put them in order.
I would like to see what the prevailing thoughts are.
Again, I'm not asking to be taught just asking what you think it does.

 

[OREGUN]

Holds the bullet.

 

[WeiserBucks]

I've got a feeling this thread is going to go full retard and I'm in.

 

[alfmoonspace]

Hold the bullet from falling out/in.

Too much or too little may cause issues. Consult with your local doctor if you have ED issues by gripping too tight.

 

[Wheres-Waldo]

Holds the bullet.

Agreed.

How one achieves his/her desired neck tension is where shit gets funky.

Standing by for full retard. @WeiserBucks

 

[SicVic]

I've got a feeling this thread is going to go full retard and I'm in.

You know I wouldn't have posted this if I wasn't ready for the ride...

 

[acudaowner]

I thought it was the point where you either enjoy sex or black out from lack of oxygen no ?

 

[SicVic]

Holds bullet! Ding ding ding
Hard to argue against this being the primary job right.
What are some other thoughts?

 

[SicVic]

So I see we are beginning to hint around at grip (perv term) or amount of tension.
Acudaowner, if we can keep you conscious long enough to answer if the amount of tension matters...??? Aside from blacking out.

 

[SicVic]

what is another thing to mess with requiring even more expensive gear to set just right Alix ?

Bang! This man right here is genius!
I need a new belt fed AMP press, I need a $300 comparator that matches the exact position the ogive contacts my barrel and so on.

 

[spife7980]

Holds bullet! Ding ding ding
Hard to argue against this being the primary job right.
What are some other thoughts?

Well when people have good results on the entire spectrum from soft seating to crimping its hard to point to anything else.

 

[FLIGHT762]

Holds the bullet.

 

[SicVic]

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??

 

[spife7980]

Youre asking for a one dimensional answer to a many dimensional question.

If you did proper development on both then you wouldnt be loading them the "same"

So it depends.

And .003 isnt a measure of tension. Its a measure on interface fit. People on youtube just use terms incorrectly and it becomes slang.

 

[FLIGHT762]

You know I wouldn't have posted this if I wasn't ready for the ride...

Here's your Horse, saddle up.

 

[SicVic]

Youre asking for a one dimensional answer to a many dimensional question.

If you did proper development on both then you wouldnt be loading them the "same"

So it depends.

And .003 isnt a measure of tension. Its a measure on interface fit. People just use terms incorrectly and it becomes slang.

I like that.
The interface fit would provide a resistance that could then be measured as a way to replicate the action if one desired.

 

[spife7980]

I like that.
The interface fit would provide a resistance that could then be measured as a way to replicate the action if one desired.

Interference would provide one dimension. Its easy to measure that.
You didnt want links but you should read this link

You are being redirected...

All of that makes up bullet grip and its really really hard to measure outside of a lab. Numbers 6 and 9 are particularly hard to quantify your control of for consistency.

 

[SicVic]

What results would I be expecting if the neck tension was on the high side as opposed to low.

 

[spife7980]

Increased chamber pressure during the initial firing. Maybe thats too much, maybe its not. Depends on all the rest of the details of the load.

Maybe thats good for where your barrel and bullet like to be for optimal accuracy, maybe its not. Cant guarantee anything

 

[alfmoonspace]

It's looking for an absolute answer to a non-absolute problem. I have seen annealed brass blow apart (head case seperation) because the neck tension was ridiculously tight.

 

[SicVic]

Interference would provide one dimension. Its easy to measure that.
You didnt want links but you should read this link

You are being redirected...

View attachment 7711521

All of that makes up bullet grip and its really really hard to measure the actual bullet grip outside of a lab.

You Sir are a facilitator of good information information and I appreciate that.
I'm after the ones who call out new reloaders and tell them "it has to be this way"
In reality, it pretty much stops at " it holds the bullet"
After that, situations dictate.
I'm here just to see how some process the importance and functionality of neck tension.

 

[spife7980]

You just want enough to be secure enough for your goals without disrupting the bullet jacket and core and making it off balance.

 

[SicVic]

Whew, finger getting worn out.
Yes, no definitive answers. That's the truth. Agreed and my beliefs.

 

[SicVic]

You just want enough to be secure enough for your goals without disrupting the bullet jacket and core and making it off balance.

This is really good. Let's say you expanded the mouth just to the point where you could seat a bullet with your fingers. Just enough tension so it doesn't fall down inside with the case standing upright.
I know you would have to insert it by hand as you're not stripping it otta the magazine but what would you expect from the results compared to the others that you seated the way you normally do?

 

[spife7980]

Way back when I initially started with my little lee hand loader that you used a mallet to neck size and seat the bullet with I noticed that some times when I would fire the next round in the magazine would have the bullet shoved all the way into the case. I had fired those poor reminton 3006 cases so many times to what was obviously just minums at best but over time the necks were thin and hard enough so that the little die didnt do enough sizing to be more than tangential contact, it wouldnt move from just touch but you could push it out. I would just pull the bullet back out to be in the neck to some little pressure and they never shot unsatisfactory to my standards. Obviously my standards were much more lax than they are now so I cant quantify it.

 

[SicVic]

It's looking for an absolute answer to a non-absolute problem. I have seen annealed brass blow apart (head case seperation) because the neck tension was ridiculously tight.

Alf, I think I can believe this could happen....
This is one of the examples I was looking for.
In short, neck tension increases pressure due to restricted force on the bullet.
I've also heard that tension aids in facilitating powder burn providing a improved bullet launch.
So we should see a pressure decrease if light tension is used?

 

[GrumpyOleFart]

Do you leave reloads on their side?
Left or right?
It matters for rifles and scopes, so it should follow that it matters for rounds as well.

 

[SicVic]

Neck tension is as much the problem as the solution.
First, zero neck tension is not practical.
Those hotdogs that like to rip that bolt handle like it's a reciprocating saw blade would have their rig blown apart from a deep seater in under 5 seconds.
I like to test stuff and have the facilities to make it, walk it to the gun and shoot it.
I've been working with "no tension" seating. It's nothing new as Alf pointed out.
What's been interesting is how it dispels a lot of common beliefs.
Tension causes problems and not just at home...
Difficult to measure, tough to replicate, concentric issues, various questionable intell, Manufacturers bidding the next big toy. Quite a challenge.
I find that if I compare two exact test sets with jump set at touching lands, one with tension and the other without.
The zero tension set produces a lower SD, a better group, a slight velocity increase (avg 10 fps) and the same poi (after velocity difference adjustment)

Again, not practical but it does hold it's ground against those who say " it has to be this"

 

[SicVic]

D

Do you leave reloads on their side?
Left or right?
It matters for rifles and scopes, so it should follow that it matters for rounds as well.

Did you know that you were Internationally Grumpy as Ole is used in both Spain and France...
As far as the side... Left. Military always starts with the left.

 

[SicVic]

Alright, that's it for me.
Wife just texted so I gotta hurry up and act like I've been doing something productive.
Once I get the video edited I'll post it here.
Gotta give the haters some hate candy for Halloween.
Thanks to all for your thoughts.

Vic

 

[GrumpyOleFart]

D
Did you know that you were Internationally Grumpy as Ole is used in both Spain and France...
As far as the side... Left. Military always starts with the left.

Cheers.

 

[Carlos Danger]

Neck tension is just a simpler term for the coefficient of friction between the two dissimilar surfaces of the bullet and the case.

 

[Aftermath]

Neck tension is just a simpler term for the coefficient of friction between the two dissimilar surfaces of the bullet and the case.

Look at you being all syllaballistic and shit.

 

[918v]

The purpose of neck tension is to give noobs an idea as to how to prep a case for bullet seating so they don’t fuck it up.

 

[jeffpatton00]

You just want enough to be secure enough for your goals without disrupting the bullet jacket and core and making it off balance.

Another factor is that insufficient neck tension can result in bullet movement due to recoil and other forces unique to semi-autos.

 

[spife7980]

I feel that was covered under the “for your goals” part of what I said

 

[sirhrmechanic]

Its why I invested in a massage chair.

Sirhr

 

[sirhrmechanic]

Another factor is that insufficient neck tension can result in bullet movement due to recoil and other forces unique to semi-autos.

Not unique to semi-autos, though. A heavy recoiling bolt gun can move an improperly tensioned bullet.

Very common when people load .303 for Enfield SMLE rifles using .308 bullets… when the Enfield uses .311-.312 bullets. No neck tension and the bullets pack up in the case… and no land engagement, so they can’t hit minute of deer at 50 yds.

Does neck tension matter? Yes. Should it keep you up at night… no. The primer
Alone will pop a bullet out of its case. The neck tension is a factor, but not a critical factor, in internal ballistics.

Sirhr

 

[hafejd30]

I’ll second everything @spife7980 said

My noted goal/reasoning would be:

- Consistent round to round tension. Which contributes to consistent seating depth when you press the bullet in

- Enough tension to hold the round for your desired use.

*Some fclass guys soft seat a round. So it fully seats when it contacts the lands. Giving a “fresh” tension on each round (much like guys who seat them a bit off where they want them then fully seat them before a match.) Also ensures each round is just touching the lands

*Some bolt guys target .0015-.0030 to be consistent and hold the round under recoil/chambering from mags

*Semi Auto guys run heavier tension to keep from the round moving under the recoil of a carrier etc

-Some also run bushings/mandrels etc to keep from overworking or minimize the working on the neck of the brass. Tight chambers with minimal tension obviously work it the least. Sloppy chambers and heavy tension/crimps on semi guns are likely to work it the most. Which can shorten the brass life especially without annealing

 

[6MT]

Neck tension is just a simpler term for the coefficient of friction between the two dissimilar surfaces of the bullet and the case.

It also stops the powder from spilling out.

 

[Scottfree92]

I think the short answer is that neck tension is how tight the bullet to case interface is. The very important fact is that this interface value must be able to be repeated time after time for any type of shot consistency

 

[Dthomas3523]

Just chiming in that when you set the jump at “touching lands” that will change some things.

The primary resistance is now always the lands. So generally speaking, you should see better results with less interference fit and/or friction (as it’s already been pointed, we were dealing with many factors in “neck tension”).

Once you back away from the lands. Then it’s going to change a bit. The entire spectrum of “neck tension” is going be in effect as the initial resistance upon primer strike is the “neck tension.”

Simple answer: find the amount of “neck tension” that doesn’t allow the bullet to move under the conditions you run the rifle in and also maintains a consistent release. Generally speaking, it’s a sliding scale. Change one thing and you’ll likely have to adjust another to maintain the consistency.

 

[JoshPutman]

Grip, like the difference between pink and purple.

 

[Wheres-Waldo]

The very important fact is that this interface value must be able to be repeated time after time for any type of shot consistency

So, I think we can/have vaguely defined what neck tension in. The interference fit between the bullet and case neck, also with regard to more obscure topics like “grab” (how grippy the interior of the neck is), “cold welding” (the interaction between two dissimilar metals), uniformity of neck wall thickness and it’s presence on the outside vs. inside of the neck, and elasticity of the neck (a factor of times fired/annealing regularity).

All of this is good and well... but how does a reloader enhance consistency across loads?

Cold Weld - Easy, either load close to the match, coat bullets or seat them long and reseat before the match/session.

Neck Wall Uniformity and location - you can measure this, and it is a variable you can control via neck turning and mandrels. How much variation is too much depends on accuracy expectations, and there probably isn’t any hard data on variation and it’s correlation to bullet release variation. We can all agree that a consistent radius on the interior of the neck is more beneficial than a consistent exterior radius (mandrels to push inconsistencies outward).

Elasticity - Also controllable via a suitable and equally importantly... repeatable method. No, your BIC lighter, nor your drill and a socket would be considered repeatable. For the crowd that anneals every “X” firings... Is iteration 2, 3 & 4 the same as freshly annealed necks if you anneal every 5 firings?

“Grabbiness”- Many things effect this variable. Dry tumbling vs wet tumbling vs no cleaning have an effect. Bullet coating has an effect. Neck tension, thickness and elasticity have an effect. Annealed vs not annealed for that particular iteration has an effect beyond elasticity. In my opinion, with everything else being ideal, this is the biggest wavering variable from one loading session to the next. Control this to the best of your ability by doing case prep the EXACT same every time. Brushing necks will help, as will a dry neck lube. Annealing every time will also help vs annealing every X firings.

Main point is this; that you may not have a grasp on everything that influences the total effect of your neck tension, but the more consistently you prep your cases, the better off you will be in consist neck tension and bullet release.

 

[semperfireloading]

So I have my opinion and I load accordingly.
I talking about a bolt gun ( mine is 6.5 CM)
Please don't write a novel or attach a bunch of tutorial links; just a few quick highlights will do.
If you think it does 3 jobs then put them in order.
I would like to see what the prevailing thoughts are.
Again, I'm not asking to be taught just asking what you think it does.

Here is general answer:

1. If tension is too low, then you will get bullet setback badly because when loading bullet into chamber the bullet will push far down into the case (if its not compressed). This will be common in AR15's if you do too little tension because of the angle the bullet goes from magazine to chamber, length of bullet matters in this...obviously.
2. If tension is too low, and its the other way, or compressed load, your OAL will grow, or the bullet will just fall out (If powder is up in the neck and its that compressed)
3. IF tension too low and bullet OAL grows, it might put bullet into lands, and cause pressure spike.
4. If tension too tight, more than say.... .04, which is more than normal, because normal would be .002 or .003, and benchrest might be .001, your accuracy will suffer slightly because ES will vary more.
5. If tension is too light, and seal not tight, it might not be sealed great and moisture could possibly get in, rare but possible, and that would be very light tension under .001 I would guess.

generally speaking, seat to .002-.003 neck tension for normal shooting applications.

This is strictly about neck tension, I did not mention crimping, which is a totally different topic.

I hope this helps. Sorry about the mean people. They didnt get enough bullying skinny geeks in high school, so they troll forums waiting for people to post basic questions, that they think everyone knows.

 

[SicVic]

Being a Marine I can handle being kicked around a little bit...as long as its not from the Navy Dudes.

Very detailed explanation and informative references!
Towards the end of your posting you referenced tension amounts (.004", .002", .001") and associated the .001" tension with a Benchrest shooter.

Do you think that lighter tension inherently produces more accurate ammunition? Just asking your opinion or thoughts on this.
Don't go overboard as I know this subject can get really drawn out.

Vic

 

[SicVic]

Just chiming in that when you set the jump at “touching lands” that will change some things.

The primary resistance is now always the lands. So generally speaking, you should see better results with less interference fit and/or friction

Do you load touching the lands?

 

[semperfireloading]

Being a Marine I can handle being kicked around a little bit...as long as its not from the Navy Dudes.

Very detailed explanation and informative references!
Towards the end of your posting you referenced tension amounts (.004", .002", .001") and associated the .001" tension with a Benchrest shooter.

Do you think that lighter tension inherently produces more accurate ammunition? Just asking your opinion or thoughts on this.
Don't go overboard as I know this subject can get really drawn out.

Vic

If benchrest does it, that means if you are benchrest, you should do it. This has been heavily studied. non benchrest, its not good. as I said

 

[chevy_man]

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??

If you can push them in by hand, they're probably not going to stay put during recoil in the magazine.

If you live in a high humidity area you'd better have something between the cu and brass or you'll have varying degrees of force required because of the corrosion.

 

[semperfireloading]

Unfortunately, testing neck tension .003 vs zero tension wont work, because the zero tension will be ES all over the place. As it cant keep OAL, and is variable. So what I think you meant is basically .001 vs .003. There are too many variables in handloads to determine outcome of such a test unless you do it through say 10,000 rounds maybe. or very high number in climate controlled conditions.
I have already tested it, many times, and did not a page about it because results in small lots are completely inconclusive.
www.natoreloading.com
I load extremely precisely, with some of the best equip money can buy. Virtually no run out, neck turned, and measure internal capacity of the brass for tests. Basically, .001 neck tension is about ~30-40 PSI of seating pressing in a 223.

Those are a few of my presses with chamber die. Runout is less than 1k, and I shot dozens of groups with 30-40PSI neck tension, neck turned brass vs 60 PSI, 80 PSI, etc. There is no conclusive "Oh, I see now" moment, and the national match guys got same result. Guys tinker with this, thinking, "oh, the round with the variable neck tension is going to be the flyer". Its not the case. There is too many variables involved to say neck tension alone makes accuracy. You wont know whether its neck tension, or the bullet wasn't consistent BC, or 10 other factors. Its too complex. The best you can do is make everything as consistent as possible, and then practice your shooting skill.