change of neck tension

Since a couple of my rifles shoots like a dream, before I SS tumbled, and have been using the vibratory tumbler and have seen some carbon on the inside of necks before I seated them. Now after SS tumbling, there is no carbon on inside of the necks at all, will it affect accuracy? Will it affect bullet tension? Wondering before I load 100 rounds for each rifle.

It could affect accuracy and it will effect tension. No hard and fast rule here...couple things you can do to help combat it....run an expander in the case or use bullet/neck dry lube.

Good luck.

Yes, you will see a major difference. The carbon build up helps act like a coating that allows the bullet to slide into the neck and create a consistent smooth surface. When you SS clean the brass, it removes the carbon and gets the brass back to bare brass. Add in the cleaning solution and the necks become more "sticky". The guys that I shot competitions with that were running SS media, had very high ES (extreme spreads) in their ammo. You would see vertical stringing issues at 800+ yards, simply due to the SS cleaning method. Most went back to walnut or corn cob because of this. But their brass was super clean! SS media has it's benefits, but it can also have it's draw backs. It's not for me.

Shoot some and see!

Try it and see. You won't know until you try it. Try the neck lube for assistance. I have a white powdered mica I sometimes use for really firm necks.

I know, I reacted too soon. Going to make a 10 round sample first. Thanks

So do ammunition companies inject carbon into the necks of their ammo when they load it. No they don't. I fail to see the difference between
new brass and ss cleaned brass. And how does one measure neck tension. Who makes a neck tension measurement gauge?

The bare metal in neck (Brass) could be causing Galvanic corrosion with bullet (copper [dissimilar material] ) or Cold Weld as RR has discussed. Add in some of the corrosive acids used to make nitro powder. I Don't' know if any commercial ammo is loaded with something on bullet or neck to inhibit corrosion. But lot of military ammo has a black tar like substance at the neck / bullet juncture. This could be a sealer or corrosion inhibiter such as No Corrode ?

https://www.nace.org/Corrosion-Central/Corrosion-101/Galvanic-Corrosion/

There is no way to actually measure neck tension.

You can measure the inside diameter of the neck, as prepped for seating, and find the difference between the ID and your bullet's diameter. This is often referred to as "neck tension," but it really is NOT neck tension...it's the just the difference between two linear measurements. It may or may not be useful, but realistically all you have is a linear difference. That does not take into account the current temper of the case neck (as in needing annealng or not, or somewhere in between), the thickness of the neck material, or the absence or presence of anything that might influence friction---such as the carbon deposits Chad brought up.

There IS a tool that will actually help you measure the force required to seat a bullet. I think it's made by Bald Eagle, but don't quote me. This might be the best most scientific way to try to quantify neck tension (too difficult to account for friction), but it still is not a bona fide tension measurement. It might just have to do, though.

RiverRider ain't wrong.

M16,

Do ammunition manufacturers produce ammo as high quality as expert hand loaders? Absolutely Not! Expert hand loaders sweat everything if they are searching for a certain level of precision. Judd, in Bench rest, sweats more than I do. I sweat more than the average hunter. It is a linear scale. I'm on one end of it, and have requirements, and due to my requirements I prefer second fired brass, with some carbon in the neck, and processed to my standards.

The end result is what I want it to be. Therefore I maintain my stance, that I really do not like virgin brass. In fact, I call it a great win, that I purchased 500 pieces of once fired 6.5 Creedmoor brass for $0.50 each, shipped. It's less money, and better brass than virgin brass. It has carbon inside it, and I can set head space for my chamber.

How do you do that if the chamber it was fired in is shorter than yours?

That's my point. We hear all about neck tension but nobody has a way to measure it. So how do they know? They don't.

I Can't if the chamber was shorter than mine. I'm still in better shape than virgin brass, which I guarantee has a shorter head space than my chamber. But my barrel was chambered with a "match reamer" that I purchased. Odds are greatly in my favor that I can head space it to my chamber.

M16, I have done load developments with virgin brass, my mistake, and I have seen 3 shots in one hole and was doing cartwheels and resized those brass and used the same charges, next thing I was dumbfounded. They did NOT shoot the same, why? Volume of the brass plus carbon in the necks is what made it shoot different from bare brass that was never fired. So I had to redo my development with fired brass with carbon inside the necks until I found my loads. I do not clean all the carbon out of the necks, just a little swipe with a brush. Hope that clarifies things up for you. Reason I posted is that it popped up in my mind that I may have this issue and did not want to waste my efforts / time yet until I do a 10 shot sample with SS cleaned brass and see what results I get before loading up 100 rounds of my shoot lights out load that has carbon inside the necks. I have always used the vibratory tumbler which do not clean carbon off the inside of the necks, they only clean the outside. I just bought the SS tumbler last week.

We can measure neck tension by "feel" when we seat bullets. It's why I figured it was time to buy an annealer after brass was fired 5X because some were soft seating than others. I don't need a tool to measure neck tension. Just the bump back measuring tools to bump shoulders. Caliper to select bushing size.

That's quite a talent that you have. Does every bullet you seat have the same tension? Is every bullet exactly the same diameter? Is every case mouth exactly the same?

I surprised nobody has come up with a way to measure neck tension. Seems like it would be easy enough. Maybe a machine with an inertia type bullet puller system. Count the whacks that it takes to release the bullet?

After I annealed, the seating felt a lot more consistent than before I annealed. I am not going to measure each bullet diameter or each case mouth, I only use Lapua and Norma brass which are one of the best brass out there. I just rather do what I know and what others do and load and shoot. I am happy when my guns shoot .2 to .3 MOA at 300 yards. If I have a question or some thing I am not sure about, I'll ask questions. I am not saying I am McGuyer or some guru but I have reloaded for 25 plus years and learn from my mistakes, I still read and do research and I am still learning from good guys on this forum and glad to have them here. Hats off to you all.

I hear you. I've been at it 40 years. The nice thing about reloading is that you will never figure it all out. I guess I'm at that stage where you wonder if doing some things are really necessary and some things are actually taking a step back. And I want proof that corncob tumbling is better accuracy wise than ss pins. I still do both. Only use the ss pins when the brass gets really dirty. I think you hit the nail on the head with the annealing.

I've been reloading since '65, but that's why I'm on here a bunch. I learned something on this thread!

There are different ways to measure neck tension...if you measure a piece of brass after a bullet is seated and you subtract from that measurement to size your brass you are creating neck tension. Don't believe me...lower it by .006 and watch the brass jacket peal back from the bullet. I'm not saying you have .006 of neck tension but I'm saying you have more neck tension than you do than if you use a neck diameter that is .001 less than the measurement. If you necks are straight and the circumference is consistent (neck turned) then it should be consistent pressure.

The other way is measure bullet seating force and that is either a 21st Century hydraulic arbor press or a K&M arbor press. I actually prefer the 21st Century...I have both and they are both consistent I just like the 21st Century a little better.

I cannot agree more.

Being nitpicky...I would say you're still not measuring neck tension, you're measuring seating force. That's analogous to estimating pressure by measuring velocity, and that's not a completely invalid approach.

Agreed. Tools are available to measure the force needed to seat a bullet. But to measure neck tension you would need to measure the force needed to move the bullet out of the cartridge case. I agree that being consistent would help in that respect. But not all bullets are exactly the same diameter. Each piece of brass is not exactly the same. And then you have variances in powders and primers. All have an effect. A nitpickingly minute small effect but an effect none the less.

If you buy good bullets then you don't have very many that aren't the same diameter (less than 5 per 100) and if the brass isn't the same that is my fault or there is something internally wrong...that will show up on the target and if you mark a piece of brass that consistently misses....throw it away or make it a fouler.

I know what you guys are saying but I'm telling you there are ways to measure it and if you use those methods to make your ammo consistent....it will make a difference on your target. Now, admittedly and as JG mentioned above....you have to determine when enough it enough and I will admit I have an OCD issue and my game is a lot different than being minute of deer @ 100y.

I think what we really need to clarify is that we want consistent bullet pull . Neck tension itself would not provide it if there was variance in the lubricity inside the case necks.

If you could measure the strain on case necks after the bullet is seated, then you WOULD be measuring tension. You CAN measure seating force, and that should be a good indicator of neck tension. But it still is NOT a neck tension measurement.

interesting discussion , but I am of the camp that this does not make any difference

IF

it's "uniform" across all loaded cases

Precision is all about being Uniform and repeatability

If the neck tension is say 20 lbs, consistently then it's going to require same
force to overcome it (uniform)

I anneal my cases every time, this guarantees that my neck is uniform in stretch
I use a bushing die that is exactly .001" smaller then my loaded case neck
I clean my brass with SS pins ( so the surface is uniformly cleaned , no variation in carbon deposits from case to case )

recent load testing with
CADEX CDX-30 6.5 mm Creedmoor
Hornady brass, Lapua 139 gr, Varget

400 yards, calm wind, best group .5"
in 20mph 3 o clock wind, 1.25"

I think that's good enough

I would concentrate on Wind reading - that's one area I cannot say I am good at
or be Uniform about prediction

I don't have the ability to sweat this stuff this much. Due to the numbers of pieces of brass I deal with every year.

.22-250, 500 pieces
6.5 Creedmoor, 500 pieces
7mm-08, 500 pieces
.308, 200 pieces
7 Rem Mag, 200 pieces

So each year in loading and shooting a total of 1900 pieces of brass, and a 6.5 Creedmoor, 7mm-08, .308 Win all get loaded and shot more than once, further increasing the numbers.

I use good brass, that I've uniformed. I clean and anneal on a routine, and I use good bushing dies. I've done all I'm willing to do to make the brass be the best I feel it needs to be.

My approach to reloading is really two different gigs. I enjoy the science of it and learning the whys, ifs, and buts. I guess I'm smitten with all the learning. In my actual reloading activities, it's all a qestion of what's worth doing and what's not. Since my focus is almost all factory sporter rifles, there's a definite point of dimimishing returns.

I'm a bit of a stickler when it comes to precision of expression. I goof from time to time for sure, but the habit of precision is engrained in me mostly due to my occupation. Misstatement will land me in uncomfortable spots more often than not. I don't bring that here to create conflict...I just see the value of crystal clarity.

I can understand the "want". I enjoy precision, obviously. Ive been getting the last bit of virgin brass fired for the 7 Rem Mag lately. Just doing my daily, off-duty rifle training. A cold bore shot 500 yards or more. The virgin brass is pretty darned consistent shooting, though not as consistent of fired brass. And the fact that I know my shoulders grow .014" from virgin to fired, fired brass makes an amazing 60 fps more.

I was teaching yesterday and i was helping my customer try and hit the little 1 MOA steel at 600 yards. Well, it was a stout, variable north wind yesterday (A gift in August) his 6.5 Creedmoor was left of the targrt, right of the target, back and forth for lots of rounds. We decided to let his barrel cool. He said "I wonder if your 7 Rem Mag can get it done". I said maybe I'll get lucky. Cold bore, 6" plate, at 600 yards. I said "Now that's fun!"

Point being, it takes lots of work at the loading bench to be able to do that. Then it takes paying close attention to external ballistics and watching for repeatability. I've got to start all over again getting DOPE on second loaded brass
By next week, when I will have shot up all that virgin brass, and load back with a .003" shoulder bump. It's supposed to create an additional 60 fps at the muzzle, since that is what it did two years ago on fired brass.

you're doing it right

It would be interesting to kmow what you find, surprises or not.

Old DOPE on fire brass created 3030 fps MV in the calculator. The DOPE I'm running on now is with 2970 fps MV. Not using a chronograph, but working the corrections backward into the calculator to make things match.

I'll let you know what happens going back to fired brass.

Tack Driver, if you have good chrono data for your load with previous case prep, when you shoot your 10 shot test group over the chrono you will have a comparison. You should then tweak your load to get the same average velocity that shoots so well and see what happens. A common theme I have found is lowest ES is often found just below maximum pressure. When that charge is exceeded, velocity often looses consistency. An increase in neck tension on a load that already has its back against the wall can be enough of a pressure increase to bump you over the pressure that is giving you the consistent burn rate and pressure needed to achieve the low ES you were getting. With precision ammo, when something is changed it is necessary to re-work things to re-create the same dynamics that performed for you. Sometimes the change will be workable, other times it needs to be scrapped.

I wasn't going to comment since the BS is getting deep and I'm not wearing my rubber boots. But yes, you can "measure" neck tension. There are multiple methods to measure it. The most common method (and easiest) is figuring out the neck tension in .001" increments. On most of my 6.5mm calibers, you have a loaded round diameter of say, .292", and I size with a .289" bushing, I am putting .003" neck tension on the case. This is simply measured in .001" increments, that's all. It gives you a consistent "number" to size your brass to, and return to the same neck tension on future reloads. If I want more neck tension, then I get a smaller bushing for more neck tension. In this case, I am measuring it in .001" increments. It is measured and will apply more or less neck tension on the bullet if I want to, by going to a smaller or larger bushing. By increasing or decreasing the bushing size, I am getting more or less neck tension. Exactly the ft lbs of force holding the bullet in place- I don't care. What I want is a consistent and repeatable neck tension from round to round. What "specifically" the force needed to pull a bullet from the case is, not sure, but it's not a lot. See my next method...

The method most on here are speaking of is the amount of force needed to remove a bullet from the neck of a loaded round. How much force or energy needed to remove a bullet from a case. This could be accomplished, but you would have to have a gauge on the press when pulling a bullet to measure the amount of force when pulling it out. I have pulled enough bullets with an RCBS collet puller to know there is certainly a difference in tension in pulling certain bullets out of various loaded ammo. When I have pulled bullets on my personal ammo, it does not require much force at all. I keep my neck tensions in check, and know specifically what I want, and load to that figure each time. This keeps my ammo very consistent from lot to lot. I have pulled factory ammo that required A LOT of force to get the bullet out of the case. Why? Virgin brass, crimped case mouth, bullets scratched up during bullet seating from rough case mouths on the brass creating more neck tension between the case mouth and bullet surface, you name it.

If you were to pull bullets on virgin brass and compare pulling bullets on fired brass (that has a carbon build up from being fired), the fired brass with the carbon build up would certainly have an easier force to remove the bullet out of the case. The carbon build up allows a barrier between each surface for the bullet to slide on, or release from. The kinetic friction between the bullet and fired case will allow it to be smoother, requiring less force.

Here's the main point- On virgin brass, there is an element of metal fusion or cold welding happening. This cold welding is between the brass case and copper bullet. What is cold welding- "is a solid-state welding process in which joining takes place without fusion/heating at the interface of the two parts to be welded. Unlike in the fusion-welding processes, no liquid or molten phase is present in the joint.... It was then discovered that two clean, flat surfaces of similar metal would strongly adhere if brought into contact under vacuum.....The reason for this unexpected behavior is that when the atoms in contact are all of the same kind, there is no way for the atoms to “know” that they are in different pieces of copper. When there are other atoms, in the oxides and greases and more complicated thin surface layers of contaminants in between, the atoms “know” when they are not on the same part...."

So, copper is one of the main metals this cold welding happens to. What's brass made out of...? About 70%-80% Copper and the rest zinc and other metals. What's the outside of a bullet made of...? Copper! So, there is certainly an element of cold welding happening on virgin brass. This same process is happening on brass that has been cleaned so hard that the brass case is now back to it's brand new finish. Measuring bullet tension on a loaded round with virgin brass and a copper bullet would certainly have more tension than if you loaded it on a fired case (keeping the measured neck tension the same, by .001" bushings).

A lot of competition shooters would load their ammo days before, and load the bullets long. Right before a shooting match, they would seat the bullets deeper to the proper seating depth. This seating right before the match would help break the cold welding happening on virgin brass. This issue is there, and it is a known problem.

Well stated sir. Thank you. I know scraped the ss pins but I never did enough work to say I could not get the same consistency

Oh snap...Chad brings up cold welding...now this thread has some potential. Don't you know Chad that isn't something that exists

FWIW...I have convinced myself through TESTING that something happens on loaded rounds that sit. Call it what you want, but something is going on. I can prove it to someone but they have to be sitting with me and I have to have old and new ammo to demo with.

Bottom line to everyone....there is a lot of good info in this post and others on this forum but don't take any of our word for it....go TEST that is the single best piece of advice I can give anyone....convince yourself one way or the other thru testing, burning powder, primers, barrels and bullets.

Yeah, I'll go as technical as needed. But dang! I got my rubber boots on now!

Smokey Bear and TackDriver,

I'm not saying don't use them. There are many people who use the SS cleaning, and it works just fine. But you just need to know what the issues are when using them. If you work up a load this way, and keep doing it this way, it will remain consistent for you. If you switch back and forth from SS media to corn cob/walnut media, you will see a difference in your ammo between the 2 brass types. The SS media is not for me for multiple reasons. Mainly, because I don't want to mess with the pins and water, and have to dry them out. I like throwing brass in corn cob and/or walnut media and turning on a tumbler and letting it run for 8 hours. It's simple for me, and quick. Plus, for competition shooting, the other issue of high ES numbers on the ammo.

Skip the rubber boots and go to the hip waders or chest waders

Dissimilar metals touching will create a small electrical current between them, some metals more current than others, under pressure such as neck tension or through manufacturing techniques and metal choices we take advantage of it every day, ever hear of a thermocouple.

I could be completely off base but a brass bullet in a brass case I doubt would "cold weld"

An insulator like powder fouling could very easily reduce the metal to metal contact and reduce cold welding.

It has been almost 30 years I designed and built a fixture to test and qualify Thermal Electric coolers for optical transmission device lasers for Rockwell International. Testing 100 at a time using thermocouples to measure the temperature on the cold side of the TECs. We used the same metal contact for all "copper" since it was handy, cheap and available. The measuring thermocouples were held in place by pressure on copper sandwiching them between the TECs and small copper plates worked quite well and was repeatable.

Over the course of testing through temperature extremes in environmental chambers there was a little evidence of cold welding within the fixture. TEC to copper when changing them out after the first batch testing there was a bond between copper and thermocouples but since it was consistent throughout it worked well and was calculated for.

All that to say I fully believe there is a Cold weld that can take place between dissimulate metals. How much between gilding metal and brass I do not know.

Sorry for the long post but brought back memories of a fun project

Bottom line in reloading we try to take out as many variables/inconsistencies to produce the most consistent loads we can. It is a never ending quest for some while others myself included work on the theory get it good enough for our purpose.

Unlike some I will clean brass if it has gotten in the dirt but if it has some tarnish from handling but is still clean I will load it up and shoot it. With tarnished but otherwise clean brass I have at least according to my chronograph had many loads in the single digits ES and most of those shot little for me groups. Some of the best shooting loads I have ever loaded were with brass on its third loading without cleaning, the only thing that was bright was the bullet and primer, I do run a plastic brush through the neck to remove some of the lead fouling though. Sure they don't look like new ammo but as long as they perform I am happy.

I am not OCD

When you speak of linear dimensional changes, you are talking about strain.

Two different animals.

I'm literally in the trust mode with cold metal welding, trusting Judd, and Chad. They've seen the results, and they are the two guys I ask questions, if I have them.

But I am fighting off 21 years of being a welder. And of the tens of thousands of welds I've made, all of them required heat. It was interesting for me to learn that aluminum requires significantly more heat than steel of equal thickness. Copper welding? I've not tried that yet, but I can find a chart that is going to tell me how much heat, via amperage, it would require.

I'm simply speculating here, that in a heat weld, I am asking it to bond in seconds, thus the need for heat. In this cold weld theory, we are talking little heat (ambient air) but a greater length of time. Of course the weld will not be nearly as strong, but there may still be somewhat of a weld. I just don't know. Therefore back to trusting some people I believe know what they're talking about. So much so that I am about to slowly get caught up on loading my 6.5 Creedmoor, which really mainly gets used for shooting matches to preserve barrel life. I'm going to charge the cases the slow way I've created for myself, but seat them long, and final seat the day before I need them. Judd and I have had several conversations about this.

For those that have never seen it, there's an ongoing joke among PRS shooters, making fun of their own procrastination. Guys have stayed up burning the midnight oil, the night before a big match, loading all their ammo. And it was just because of procrastination, not on purpose. But guess what? Their ammo shoots terrific the next two days.

There is a manufacturing process that utilizes the cold weld phenomenon. On the molecular level, some of the two different materials will migrate into each other. It's not a galvanic process, it is physical.

Time and pressure make it happen. Temperature...I don't know, but based on what I know about science, increased temperature should accelerate the process.

Which is what I was saying about the weld that happens in a second, or less. Extreme high heat, extreme shortening of time to complete the process.

Interesting stuff!! I have loaded up some SS tumbled 6.5 x 284 and the .308 later today. The 6.5 x 284 have seated softly so far even with bare necks, its .001" neck tension. It's the stickiness of the bullets to the bare metal that I am concerned that may throw the way it shoots off course again. Hopefully tomorrow I'll test them at the range. Will keep ya'll posted.

Going to take the 7 Mag that I done a ladder test two weeks ago with Retumbo and 160 Accubonds for deer season before I SS tumbled. I found a nice cluster and velocity of 3100 fps which outstanding. So far I have not shot any loads with SS tumbled brass yet. Tomorrow is trial day.

The cold weld is intriguing. I'm sure there is something to it. I grew up working in my dads welding shop. In retrospect, the concept of like metals bonding to one another was nothing new to him. The term was "gallded". "Don't put those together. If you got to take it apart they will be gallded tight".
Tackdriver, when I scrapped the ss pins I was loading an old reliable 7-08 load that I used too shoot at distance with some buddies. There is usually a little low stakes wagering involved. My wallet was lighter when I left. I went back to the Lyman and corn cobb. It wasn't as consistent for me, but it was a load I had worked up with different case prep. I didn't chrono the ammo with the squeaky clean brass or try to tweak things to see if I could make it work for what I wanted. I had just got my feelings hurt and that was the end of that. So I haven't done enough work to say much other than it can change things. How it will work with your load is a try and see. Hopefully it will do well. Just don't put any money on it before you try it....

Couple things I'm picking up from reading this thread so far...

You guys are discussing neck tension, and or the tension required to seat, or even pull the bullet. One thing on this subject sticks in my mind. Let's say you close the ID of the neck up to exactly .003" smaller than the OD of the bullet for 100 rounds.. But, lets say 20 of those brass casings were trimmed SHORTER than the other 80.. Would this not have an effect on the force required to both seat, and/or pull the bullet? If you are trying to keep each round exactly the same I think trimming all brass to the exact same length each time, every time, must play a part in this. Maybe you guys already do this and that is why it was not discussed. If that's the case, my bad for being the slow one at the conference.

Next... In my mind a lot of this neck tension/bullet hold stuff can easily be lost when you think about it this way... When the primer ignites the powder, the bullet begins moving forward instantly until it contacts the lands and then provides some resistance. In my mind as soon as the bullet contacts the lands it momentarily slows down from the speed it was traveling right before it hit the lands.. At this moment, when the bullet begins to enter the neck of the chamber, and it gets tight, at that moment the pressure then blows the case in all directions such that the case is an exact fit inside the chamber. In my mind, once that case expands outward, there is no part of the cartridge neck that is still touching the bullet at all. Unless of course you have a custom chamber that is so tight that the neck of the brass cartridge cannot expand outward. My point being, once that neck blows out in all directions away from the bullet the expanding pressure behind the bullet is the only thing acting to drive the bullet further into the neck of the barrel. So, if you could slow down the firing of a round into frames and view them I think we could see this in action.


My question is, how much does neck tension really play in all of this since it is OUT of the equation as soon as the bullet moves forward enough to engage the lands? If you guys are saying that the initial movement of the bullet out of the case going towards the lands is what is being discussed as to how it affects everything that happens after that, then I can kind of see how one leads into another. It seems like such a small role, but apparently it is significant in the rest of the cycle.