Neck Tension?

[R Stiner]

Over the years of reloading the definition of Neck Tension seems to have no real definition!

The other day I was helping a friend with reloading and his thought was {see attached Pictures} was .0015 tension because you only count one side! I said its actually .003

I explained to him It is the outside diameter of bullet compared with inside diameter of sized brass. he then asked the difference between light neck tension and heavy neck tension?

Here's where it get good!

you know when you get caught with your hand in the cookie jar! and you know it might not be the right answer but it what you go with!

Light tension .002 or less
Med tension .002 to .005
Heavy tension .005 and up

So here is the question?

1: What do you say the pictures shows? .003 or .0015?
2: Is that a good definition of neck tension or not?

 

[jackie schmidt]

Over the years of reloading the definition of Neck Tension seems to have no real definition!

The other day I was helping a friend with reloading and his thought was {see attached Pictures} was .0015 tension because you only count one side! I said its actually .003

I explained to him It is the outside diameter of bullet compared with inside diameter of sized brass. he then asked the difference between light neck tension and heavy neck tension?

Here's where it get good!

you know when you get caught with your hand in the cookie jar! and you know it might not be the right answer but it what you go with!

Light tension .002 or less
Med tension .002 to .005
Heavy tension .005 and up

So here is the question?

1: What do you say the pictures shows? .003 or .0015?
2: Is that a good definition of neck tension or not?

If the case is .003 smaller than the bullet, that is .003 neck tension.

Or, .0015 to the side.

 

[JerrySharrett]

The ballistic effect of neck tension is not measured in thousands of an inch, because, not all brass has the same hardness especially after several firings. The best way I have found using a Wilson type seater to measure it isl
1) if you can seat a bullet by thumb pressure alone it is light tension,
2) if it takes the heel of your hand to seat the bullet you have medium tension.
3( if it takes the arbor press to seat a bullet you have high neck tension.

You will find, also, that a bullet seated to hard jam neck tension has less effect while a jumped bullet is more effected by neck tension.

Some powders, like V133 likes a lot of neck tension while something like Rl-10x doesn't.


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[pablo]

Think you might find that if you take a sized case and measure the neck with a 1" mike, not a caliper, then seat a bullet in the case and measure it again, then subtract your first dimension from the second you will have something accurate to discuss. Using a caliper to measure the inside of the case neck isn't a good way to find out what you really have.

 

[Wilbur]

Depends on what you want to find. If you're looking for a safe load, you can measure the loaded round. That done, if you want more neck tension use a smaller bushing.

I've tried it several ways....from zero neck clearance to way too much neck clearance. It didn't matter at all except the zero clearance created constant checking. I let my case necks thicken such that I had negative clearance and that didn't work well at all. Gene Buckys counseled me quite sternly over that matter.

 

[243winxb]

If the neck expands .002" after seating a bulllet in 223 , bullet pull is around 35 to 45 pounds by my testing. The attachment was on the internet.

 

[R Stiner]

After five reply's It looks like its safe to say there is no real definition of neck tension.

they are all good answer's!

Wilbur
I like your way of thinking! as long as you don't get in trouble!
I'll change bushing's and let the target tell me what works or doesn't work.

I will mention if you run .001 or less you will you have to change to a smaller bushing as the brass work hardens.

I used the same bushing and same brass no annealing all last season. around .004 under bullet dia. and did not see any change on the target all season.

thank for the reply's gentlemen!

Russ

 

[retired]

If you are at or in the lands,, neck tension is a minor player, you may see not change over the year.
If you are not at a top load window, maybe not as noticable.
If you are jumping long, and not at the top, you should see diff on the target,
but then there is your skill/the quality of the gun..it may cover it all up.

After five reply's It looks like its safe to say there is no real definition of neck tension.

they are all good answer's!

Wilbur
I like your way of thinking! as long as you don't get in trouble!
I'll change bushing's and let the target tell me what works or doesn't work.

I will mention if you run .001 or less you will you have to change to a smaller bushing as the brass work hardens.

I used the same bushing and same brass no annealing all last season. around .004 under bullet dia. and did not see any change on the target all season.

thank for the reply's gentlemen!

Russ

 

[MilGunsmith]

The US Army standard is minimum of 45 lbs of pull for 5.56mm (.223) with a crimp and case waterproofing. We check all ammo lots we test and find most are in the 75 to 85 lb range. I had an engineer tell me the other day that his new stainless steel case offered better accuracy because the neck tension was high, we tested different lots of cases and some where as high as 400 lbs. Pressures where also as high as 93,000psi in a Universal Receiver.

 

[GeneT]

If the neck expands .002" after seating a bulllet in 223 , bullet pull is around 35 to 45 pounds by my testing. The attachment was on the internet.

Thanks for posting that - interesting data.

GsT

 

[Apollo]

Hey Russ. How's it going?

I think the definition of neck tension is = Force holding a bullet in the case due to the bullet's pressure ring stretching the case neck.

But, is there a set standard way of measuring neck tension? Not sure. The way I was taught is to measure a loaded round over the pressure ring then subtract the neck bushing used when resizing. For example a 30 BR loaded round measured over the pressure ring might be .328. If I used a .325 bushing that would give me .003 neck tension. Is that correct? No idea. I'm pretty sure The Wizard (Bigelow) does it a different way - which is a good indication that "my" way is not correct.

However, I'm not losing any sleep over it because to me, the important thing to keep note of is that all my cases need to measure the same over the pressure ring (in this case .328) and that I am using a .325 bushing. I can try a .324 or maybe a .326 (not likely) to see if that tightens up my groups after I have found the correct powder charge and seating depth. The target will tell me which bushing to use - not a mathematical equation.

Looking forward to May in Webster.

Stanley

 

[Lee Martin]

Like others, I just mic the sized neck. Then I subtract that from the loaded round's neck diameter (mic'd). Close enough. Ultimately, that number doesn't mean much if good things don't happen on paper. The gun will tell you how much tension to use for a given powder.

-Lee
www.singleactions.com

 

[R Stiner]

Every reply has good information!

Were all looking for the same end result "constant precision on the target" we just sometimes take a different path to get there.

To achieve that! we use the tools that are available to each of us. I used the calipers in the picture for the reason most reloader's have a set.

Jackie's reply .0015 {to the side} is a machinist point of view. when I was explaining to the person I was helping I said .0015 {each side}. his reply was "what about the other two sides?" I had to read Jackie's reply a few times before the light bulb lit. I explained it wrong to the person I was helping thanks Jackie!


Jason: Just waiting for good weather to get some trigger time! Looking forward to see you in may in Webster city.
great explanation on your methods. I think the only way I can beat that Bigelow guy is to poke him in the eye!

I would encourage everyone to read this post a few times there is lot of good stuff here!

Russ

 

[Boyd Allen]

Anyone that is serious about accuracy needs to have a 1" mic. that reads to .0001. Calipers are not a good way to measure the ID of a neck. The proper way to evaluate the effect of changes in reloading procedure is by testing at the range. No matter what anyone says, or you think, whatever gives the best results is the best procedure...as long as it is safe. Beyond a certain point the elasticity of the brass is exceeded and all that you are doing is using the bullet as an expander and putting a bigger step in the neck where the shank ends.

 

[wfcustom]

Re: Neck tension

As some others have already mentioned, neck tension is a measurement of force ie:
how much force does it take to release the bullet from the case.
The relative smoothness on the inside of the case also effects the release,
you can really see this when you seat bullets and are using some method to measure your seating force. (Seating force roughly correlates to neck tension)

If you are looking for a starting point, (assuming trued case necks) the time honored method is neck thickness (measured with a 10th ball mic) x 2 + bullet pressure ring diameter - .002.
Thats a long way of saying measure your loaded round at the pressure ring and start with
a bushing .002 smaller.

In my 6PPC I use a .2645 carbide bushing on a .268 nk chamber .0114 nk thickness .2432 pressure ring on bullet. So I am using .0015 neck tension if you will, which gives me a consistent 20lbs of (measured) seating pressure on annealed necks. My 6BR is about the same tension, while my 6.5/284 & 7MM Fat Dawg use .0025-.003 of sizing for @ 40-50 lbs of seating pressure.
I also find that the more "jam" you have the more consistent the tension needs to be.
Basically you are balancing the engraving resistance on the bullet jacket with the tension.

All that said as most of the previous posters have stated it don't mean squat if it doesn't show up on target. As in all other thing BR related start with your best SWAG and then ask the rifle.

Regards,
Greg

 

[Wilbur]

Most, if not all, include the rifle in the equation. That is, the rifle will shoot best at one neck tension but not another. I don't believe that's true as the neck expands (if it can expand) before the bullet does/moves much at all. You have to get pretty darn close to no clearance at all before the cases begin to look different...as in the black marks on the case neck.

 

[Randy Jarvais]

All of the replies state forces necessary to move the bullet in a static situation. Does the case neck expand with the case upon powder ignition? If it does, doesn't that change all the pressure parameters for moving the bullet when compared with a static state? I do not have the answer. I was just wondering if the case neck expands with the rest of the case toward the chamber walls before the bullet starts forward much, thus creating a situation whereby not as much pressure is needed to release it from the case mouth as it would have been in a static state.

 

[vtmarmot]

Sounds plausible. I thought I remembered reading in Harold Vaughn's "Rifle Accuracy Facts" that the chamber expands some as well. I didn't want to leave the Bruins game to get up and get the book, but I did find a complete, searchable edition on archive.org. There are some references to "radial expansion of the chamber." Hope I haven't caused the engineering wonks out there to stay up thinking about it.

 

[Boyd Allen]

Most, if not all, include the rifle in the equation. That is, the rifle will shoot best at one neck tension but not another. I don't believe that's true as the neck expands (if it can expand) before the bullet does/moves much at all. You have to get pretty darn close to no clearance at all before the cases begin to look different...as in the black marks on the case neck.

None of us can be inside the chamber watching what is going on real time. This is just reporting. Many years back, I was shooting matches at the Visalia, discovering the nature of mediocrity, and I had a conversation with the late Del Bishop about neck bushing size. I was shooting a .262 neck 6PPC as were most of those who competed at that venue, including Del and his good friend Steve Kostanich. I was turning my necks to the then common thickness of .0086 or thereabouts, and using a .258 Wilson bushing. Del told me that Steve and he had discovered that 133 shot better with more neck tension, and suggested that I might want to give that a try. I did, a .257 and it seemed to me that my groups got better. In fact I am pretty sure of it. This is not science, or me telling anyone that based on my great reputation as a competition shooter what the truth is. It is me reporting some things that happened.

The only powder that I shot in those days was 133, some time later I happened on slightly less than a pound of Israeli manufactured 2015 and I decided to do a neck tension test. I found that it did not seem to care much what the neck tension was, that is shot just as well with very light neck tension as with moderate....but I never could get any more of the stuff, and as I understand it the factory was destroyed in an explosion. I did learn one thing that made the experience worthwhile. Not all powders are the same with regard to their "preference" of neck tension. or tolerance of it variation. At least it seemed that way to me at the time, based on what little unscientific testing that I did.

 

[Ajshooter]

Neck tension

I was shooting a 268 neck . I was using a 263 bushing with lt32 groups was mediocre. I thought it should shoot better so I I tried a 265 bushing groups tightened up quite well . I was suprized . I also found two seating depths that shoot well one at touch and one at jam.