Neck Tension Question

[Headgear]

I am loading 308 Win rounds with Win brass that I bought new and processed. they were shot twice in my CZ and then I bought a GAP custom and had to get a match full length size die to resize them down to the new chamber.

I sized all and shot them once and after they were fire formed to the new action, I went back to neck sizing them using a lee neck size die. When I seat the bullets I can feel the difference in the neck tension between one that is run through the full length die verses the neck die. Full length being a lot tighter feeling.

I'm concerned about it because a much more experienced friend came to shoot with me for four days and go over my loads etc. We found that my reloads have next to no run-out probably because of the Forster press, but the standard deviation was 34 FPS. The ones we tested were loaded for the CZ, didn't have the GAP yet, and they were all neck sized only. I wish I had a chronograph to see if there is a difference between the neck and full length size rounds.

Sorry for the long winded question. Any ideas?

 

[wirehand]

Re: Neck Tension Question

Go ahead and state a question.

 

[SPAK]

Re: Neck Tension Question

how did you get a SD of 34fps if you didn't have a chronograph???

 

[jeffm]

Re: Neck Tension Question

If I understand what you are saying, you are comparing fire formed neck sized brass to full lenth sized brass. They will not be comparable until they are fire formed to your chamber. Shoot them and see what happens. I would seperate my brass based on brand, times fired.

 

[gcoulsey]

Re: Neck Tension Question

Which bit are you concerned about exactly?

Your fps spread?
Or the difference in neck tension between the different dies?

By design, the Lee neck collet die (if that's the one your referring too)
Puts minimal amount of tension on the necks, about .002"

Your FL die is probably sizing them a bit tighter,
But neither is a problem in itself.
You just have to 'tune' your load to work the best with whichever die you ultimately decide to use.

 

[Headgear]

Re: Neck Tension Question

I guess i never did get real clear on what my concern is. Sorry about that. I am concerned that when I use the Lee collet neck size die that the neck pressure seems so light compared to the full length die. I can feel the difference when seating the bullet.

When a friend came over with his crony I shot ten through it and we had a SD of 34 FPS. Those loads had been neck sized only. I am wondering if the light neck tension is what was causing the rather high SD. Thats why I said above that I wish I had a crony myself so I could compare the full size die reloads to see if the tighter neck tension would give more consistency. (My friend lives six hours away. not so convenient to borrow his)

My actual question is, would you think that the tighter full length sized loads would have a more consistent velocity and therefore, accuracy?

I measured the outside of the neck on a full length sized casing before seating the bullet and it was .3295. The neck sized casing before seating was .3310 and a finished round is .3325. I'm not sure if that tells you anything much about the neck tension but if it does, let me know. I'm looking for as much accuracy as I can get.

Thanks

 

[Fuzzball]

Re: Neck Tension Question

"When I seat the bullets I can feel the difference in the neck tension between one that is run through the full length die verses the neck die."

Lee's collet die typically leaves necks about 1 thou under bullet diameter and that's plenty. Most others leave smaller inside diameters so, yeah, you will feel the difference. But, it doesn't matter at all.

The added seating resistace is only the extra effort required to futher expand the neck so the bullet can enter, that extra effort is NOT a sign of a tighter neck grip. Any stretching greater than about 1 thou simply exceeds the yield strength of the brass and adds nothing. Prove it to yourself; measure a loaded neck, pull the bullet and measure the neck again - THAT is the "tension" your bullet actually has, not the extra that you thought you had.

Bottom line; don't worrry about it.

 

[Headgear]

Re: Neck Tension Question

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Bottom line; don't worry about it.</div></div>

I'm sure you're right. Sometimes I get a little over the top fussing to get things just right. I will pull a bullet and see what the neck measure just for curiosity's sake.

It does still bothers me though why that SD was so high. I use an RCBS Charge Master and make sure every load is the same as much as possible, weigh and categorize the bullets, use CCI BR2's debur the flash holes and chanfer the cases inside and out. I don't get it

 

[Fuzzball]

Re: Neck Tension Question

"It does still bothers me though why that SD was so high. I use an RCBS Charge Master and make sure every load is the same as much as possible, weigh and categorize the bullets,..." etc.

Not too surprising. Sounds like your load needs some powder charge changes or OAL tweeking or a primer exchange. Not that a load with an E.S. of 2 fps will automatically shoot great, so stick with accuracy until the variations cause misses at long ranges.

Of all the things controlling speed variations the biggest - by far, IMHO - is working in the right peak chamber pressure range. The RIGHT range and that's not controlled by counting out equal kernels of powder or the other things you mention. Powders are designed to burn most consistantly within a moderately narrow pressure range. If we get outside of that range, high or LOW, the burn and speed will be inconsistant.

IF you are loading inside the proper charge and OAL range for optimum performance for your rig, the normal small variations some folks appear to sweat over become meaningless. But, load on the ragged edge of any parameter and your ammo will be quite quirky!

If you really want to see something interesting about "neck tension", measure the neck of cases sized in both your Lee and FL die, then seat a bullet in each and measure again. Compare both of those with the diameters you get after pulling the bullets to see just what a difference the two dies really make. Won't be much, if any.

 

[Headgear]

Re: Neck Tension Question

Thanks Fuzzball, You know, I got this GAP rig about three weeks ago and I have been so excited with it that I never did stop and work up some test loads and see exactly what it likes, other than checking for over pressure of course. I'm not that terribly experienced at this and again I was listening to the advice of a friend whom is very experienced and he told me that it will end up liking a load right around 43.5 grains of Varget with 168 SMK's. Not that it will like 43.5 but around there, so I really need to do some testing with charges. I have the OAL set at .0025 off the lands now. After I determine the best charge, I'll start working on the OAL too.

Last week I was shooting at 200 yards and had good consistency shooting 43.5 grain loads. I had about six, five shot groups between half minute to a minute with several that were sub-half minute. Then I went again the next day with some loads that were 43.7 and the groups opened up about another half minute or so. Now the wind was a little heavier the second day but I can't see the wind having too much effect at only 200 yards but then again, I'm pretty green at this. Maybe it was the other two tenths of a grain. I'll get to work finding out.

Anyway, if anyone has anymore thoughts on how I can get better performance, I'm all ears.

Thanks

 

[Brasscow]

Re: Neck Tension Question

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Headgear</div><div class="ubbcode-body">Thanks Fuzzball, You know, I got this GAP rig about three weeks ago and I have been so excited with it that I never did stop and work up some test loads and see exactly what it likes, other than checking for over pressure of course. I'm not that terribly experienced at this and again I was listening to the advice of a friend whom is very experienced and he told me that it will end up liking a load right around 43.5 grains of Varget with 168 SMK's. Not that it will like 43.5 but around there, so I really need to do some testing with charges. I have the OAL set at .0025 off the lands now. After I determine the best charge, I'll start working on the OAL too.

Last week I was shooting at 200 yards and had good consistency shooting 43.5 grain loads. I had about six, five shot groups between half minute to a minute with several that were sub-half minute. Then I went again the next day with some loads that were 43.7 and the groups opened up about another half minute or so. Now the wind was a little heavier the second day but I can't see the wind having too much effect at only 200 yards but then again, I'm pretty green at this. Maybe it was the other two tenths of a grain. I'll get to work finding out.

Anyway, if anyone has anymore thoughts on how I can get better performance, I'm all ears.

Thanks </div></div>

Don't seat so close to the lands. Try .010 off. You're flirting with too little GAP between touching, jumping and jamming. This is liable to cause the inconsistencies you're seeing since any small variation could lead to bigger pressure spikes. Set it back a hair more and see if tha doesn't help out.

 

[TresMon]

Re: Neck Tension Question

Hgear,

Consistency brother!! If I read correctly your concerned about the SD numbers. That is a big factor of neck tension. Tighter grip of the case on the bullet makes for higher chamber pressure and higher velocity.

So 1. don't swap around dies! Stick with the neck die. (you'll need to FL resize on occasion though.)

2.anneal your neck cases per three firings or so. Firing and resizing work hardens brass. And no, all the brass case necks will not harden to the same degree at the same precise rate, so there goes your neck tension consistency out the window, and with it your SD numbers.

3. get a "tubing mic" or if sold by a reloading company called a "neck" mic. Use it to measure the wall thickness variation at the mouth- there are lots of things you can do! read this...

http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=1696162#Post1696162

 

[Headgear]

Re: Neck Tension Question

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Don't seat so close to the lands. Try .010 off. </div></div>

Hopefully I shoot better than I type. That was supposed to be .025 not .0025

 

[mdesign]

Re: Neck Tension Question

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TresMon</div><div class="ubbcode-body">Hgear,

Consistency brother!! ....

2.anneal your neck cases per three firings or so. Firing and resizing work hardens brass. And no, all the brass case necks will not harden to the same degree at the same precise rate, so there goes your neck tension consistency out the window, and with it your SD numbers. </div></div>

+1...sizing work hardens the brass which results in it feeling like it takes more force to seat some bullets than others due to different hardness.

This article has a description to the method I use...other methods work as well.

300 WSM Load Development

While I put the paint inside the neck, I center the flame on the shoulders below the neck. Using the case holder in an electric drill, it takes about 4 seconds/case.

 

[Hummer]

Re: Neck Tension Question

Neck tension is but a small part of getting a small SD. Propellant burn rate, primer energy, barrel condition, inside of neck condition, flash hole centrality, case volume all come into play.

Mainly it is uniform bullet pull that is the telltale, not how it feels being seated but the amount of force it takes to release the bullet to move.

 

[Fuzzball]

Re: Neck Tension Question

"Hopefully I shoot better than I type. That was supposed to be .025 not .0025"

No sweat, that's what I thought. So many guys make the same mistake I've come to expect it.

 

[TresMon]

Re: Neck Tension Question

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Hummer</div><div class="ubbcode-body">Neck tension is but a <span style="text-decoration: underline"><span style="font-weight: bold">small part</span></span> of getting a small SD.

<span style="font-weight: bold"><span style="text-decoration: underline">Mainly</span></span> it is uniform bullet pull that is the telltale, not how it feels being seated but the amount of force it takes to release the bullet to move. </div></div>

So is it a small part or the main part of lower SD's?

Neck tension and "bullet pull" are directly related if not the same.

 

[Hummer]

Re: Neck Tension Question

By neck tension I mean the size of the neck in relation to the bullet. Some folks like a neck to be .002" smaller than bullet. Others .001" smaller and other combinations.

Only problem with a expander ball it depends on too many variable things that will affect the force required to move the bullet.

Some factory ammo will have a bullet pull force of around 300 lbs. The spec on M118LR only requires a minimum bullet pull of 10 lbs and no maximum on the spec. The variation of neck thickness gives a wide range of tension though the case mouth may be relatively the same size, if the neck is not absolutely uniform all the way around it will have thicker areas and thinner areas this will provide different grip case to case.

The allowable neck wall variation on M118 Match brass is .005". Ball I believe could run up to .007" variation. Thusly if you have .013 neck on one side and .018 on the other there is going to be problems with tension and bullet pull variations not to mention the bullet being introduced to the throat .005" off the center line.

As well if there is a variation in elasticity of the neck due to inconsistant stress forces in neck that will give you different pulls.

All this goes out the window if striker velocity/energy do not do their part in the ignition sequence. This will take some testing as all primers are different. Some propellants just work better with certain primers when burned in a chamber it likes. Pretty well everyone knows 308 was loaded with 4895 and 30.06 match was as well but the performance was better in the smaller case.

Load ten rounds of one primer, shoot and record SD and AV. Change primers use same brass, load etc and compare them. I have seen as much as 80 fps AV change just by changing primers.

The Marine Corps ammo room used to have an internal requirement on long range ammo of 10SD or less and they did lots of work to attain this.

Military ammo is loaded to a velocity window first. Secondly the pressure must not peak before the velocity is attained. Thirdly there is a requirement for port pressure. Thusly you can theoretically have low chamber pressure, perfect velocity window and excessive port pressure and or excessive SD and the ammo will flunk.

Take a force gage and apply slow steady force to underside of press handle with a collet puller around the bullet and watch the pounds rise and record the variation of pulls. On my tool I pretty well figured out one pound on the press handle delivered 7 lbs on the down stroke. Record the lbs to move bullet on case with Sharpie marker.

Set the ammo up several months and come back and do the same test again. Have a bucket nearby to puke in.

 

[mdesign]

Re: Neck Tension Question

Hummer - Interesting test you are outlining in your last paragraph, can you share actual data from testing?

If I understand you correctly, you are saying that it may take X lbs/force to seat the bullet but a higher amount of force will be needed to pull the bullet and that number will even be higher if the rounds are left set for a few months? I wonder why time would increase the amount of force required?

In my line of work we routinely do force testing and it is very common to see force peak at the point where the body breaks free from its static position and begins to move. A lower amount of force is required to sustain its movement once it begins to move.

Because this is consistent with the laws of physics, I would expect the forces of a bullet to behave the same way. Perhaps there is one significant difference and that is the internal pressure of combustion causing the case to expand and release the bullet vs the forces required to cold pull a bullet with a collet.

 

[Headgear]

Re: Neck Tension Question

Is neck thickness more consistent with better brass like Lapua? I need to get a neck mic, a neck turner and an annealer and I'm thinking about starting over with the best brass I can get.

 

[Hummer]

Re: Neck Tension Question

The bullet jacket tends to bond with the case. There is another thread on hide about cases cold welding with bullets I read about a year ago???? I contacted a gov't contact I have who teaches corrosion, galvanic action etc and he was aware of the problem but not alot of heartburn because the ammo still meets spec and in the event of problems rather than isolate the source, the ammo is destroyed! ! ! ! Which doesn't help us haha.

Bullet pull forces are only tested on new ammo and was so done with military match ammo. I am not aware of any bullet pulls conducted by the Ammo Surveilance Techs on ammo in long term storage. Then again with 300 lb bullet pulls being acceptable for such.................

As indicated it is loaded to pressure, velocity, port pressure, standard deviation and dispersion.
Chronograph military M118 and you will need that bucket I mentioned.

I have fired LC 30.06 Match (loaded in 60s)at 600 and had 7 ring elevation ! !! ! ! The bullet pulls on this stuff is all over the board.

I have pulled a goodly number of Match ammo rounds down and the variation in bullet pull is amazing ! ! ! ! It goes from popping right out all the way to impossible to break the seal and deforming bullet in process. Now when I pull I grip bullet about 1/16" above case mount, draw up collet and seat it deeper to break the seal then pull it out and even that the variance can be felt. It seems to be more uniform and easier to do in cold weather ! ! ! ! With ammo cold.

As well I was given a 50 cal can of carbine ammo all loaded with new componants by a guy who thought it would be needed for social work. He got old and is in bad shape and his stuff was being sold off by a friend who is a dealer and he knew the guy might not have practiced good loading practices and is afraid to sell the ammo. AND FOR GOOD REASON ! ! !! I pulled some and propellant charges vary wildly. New Sierra bullets, new Winchester cases and some is siezed so tightly that I completely destroy the bullet and never get it to move! ! ! !!

Yes once the bullet does break the force to keep it moving remains about the same but we are talking about 3 miliseconds of action time.

Action time can vary wildly between primers as well and used to be a big concern in ammo plants when we had MGs mounted on aircraft that was to be fired between the propeller blades. Ammo for such weapon systems was tested for action time and only ammo that gave 3.5 miliseconds or less was accepted for aircraft use and the ammo shipping cases so marked as acceptable for such use.

Thus my statement that there are other varying factors.

My friend Larry Moore used to say in effect, "well what can you expect when they mix primer ingredients just like your wife makes biscuits" with a big grin.

The bench rest boys figured out years ago there was variation case to case and I remember a conversation I had with Pat McMillan the barrel maker who was a BR shooter at Perry about 30 years ago. He told me he used one case in matches but had another spare in case there was a neck split and of course these were fired within seconds after being loaded.

I suspect the inside condition of case mouth would affect bullet pull if the carbon had not been removed and I haven't played around with that yet.

Also the uniformity of the stress relieving of the necks would logically have varying amounts of neck tension.

I had ammo tech friends who worked at FA and they told me in the testing they conducted that new cases gave much better uniformity than reloaded cases. But then again in those days no one knew or thought to clean their brass as is done now.
FA had a 300 yard indoor range and millions of rounds of ammo testing conducted therein. One said they pulled and marked each shot during a string and one day he had a perfect double for two consecutive shots and he couldn't wait to get the test over to check the chronograph reads for those round numbers. I think he said it was around 55 fps between the two rounds.

Also had a friend who worked primer engineering for Remington and as a result he became absolutely obsessed with primer storage in their relation to being exposed to the normal everyday variations in humidity.

As I tried to point out originally the things that can affect you are many and SD indicates bad news at long range. Larry Moore explained it this way, a one hundred foot change in velocity will give you 40" of elevation at 1000 yards so right there you need 50 ft just to maintain the ENTIRE TEN RING from top to bottom. If you want to hit the X ring you are going to need 25 fps and that is assuming your hold has absolutely no error so if you want to account for such you are going to need your ammo to shoot ES of much less than 25. As we all know, achieving that is the plan but not necessarily the result of our efforts.

Insofar as the laws of physics we had a guy in SC many years ago who was a PHD ME and he wrote this big work with forumulas to explain why it was easy to shoot one hole groups. Now this guy was very good but he couldn't do it. My Dad gave Larry Moore a copy of the study (about 30 pages long) and Larry thumbed through it and busted out laughing.

Another ME I know ran the calculations on a M1 Garand and said it wouldn't function.

Lets see MEs said the Titanic was unsinkable.......

 

[Hummer]

Re: Neck Tension Question

Headgear, don't know about Lapua but I suspect there will be some just due to the fact of mass production and drawing the cases.

If you cruise the bench rest forums as I have you have probably noticed there isn't a whole lot about anything we can use haha.

This brings to me recalling a demo made by a 1000 yard bench shooter at Quantico 25 years ago who was shooting a 300 Win Mag at 1000 in a demo for the Marine Sniper school. I had a friend who was there and he got around so he could watch the chronograph and said the guy shot two sighters and ten for group and his velocities ran like 3001, 3004, 3002, 3006, etc etc. He said he had a ES of 5 fps last ten rounds ! ! ! ! !

Now that tells me somebody knows something they ain't telling ! ! ! !

Take a good 0-1 mic that reads in tenths and measure outside necks on loaded rounds and as the Brits say "get the good news" which by translation means the opposite.
Couple that with a BFN (big f-----g neck) and chamber and....................

 

[TresMon]

Re: Neck Tension Question


Are not neck tension and [the required force to] "bullet pull" exactly the same?
neck tension is the cause and control of required force to pull a bullet.

 

[Hummer]

Re: Neck Tension Question

Here is the data I just obtained on five rounds of 308 I have had loaded for a while. Winchester cases cleaned and FL sized with neck internally uniformed.

Cases are numbered 1 thru 5. The first figure is the maximum amount of force that was required to move the bullet from the case. The second figure is the amount of force required to reseat the bullet to the same place. Note the below poundage needs to be multiplied by 7 to determine the actual force needed in each direction.

Round 1 23.1 lbs pull force. 21.7 lbs seat force.

Round 2 33.0 lbs pull force. 22.0 lbs seat force

Round 3 24.1 lbs pull force. 14.6 lbs seat force.

Round 4 28.6 lbs pull force. 20.5 lbs seat force.

Round 5 24.7 lbs pull force. 19.8 lbs seat force.

 

[Hellbender]

Re: Neck Tension Question

There was a recent article on 6br.com that was talking about huge variances on bullet seating force just by how long the brass sat after sizing.

Perfect if done within a few hours and got progressively harder as it aged (even a day or two).

 

[Headgear]

Re: Neck Tension Question

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">There was a recent article on 6br.com that was talking about huge variances on bullet seating force just by how long the brass sat after sizing.

Perfect if done within a few hours and got progressively harder as it aged (even a day or two).</div></div>

That's depressing! I like to process and prime 300 at a time and then fill them and shoot them, usually 50 at a time, as time allows.

 

[Enios]

Re: Neck Tension Question

Quite by accident last night I had been trying out my new SS media.. I had 50 rds ready to go and had checked with a bullet (tried to push it in by hand) to see if I had necked sized already.. Well had them primed and loaded and when I started to seat bullets it almost fell in... Had to pull the decapper from my sizer and would size the neck and turn around and seat the bullet... It was the most consistent feel I've ever had on seating the bullet... Will have to see how it works out, but it will change the way I do things in the future... I wont be sizing my necks in the future until I'm ready to load... Since I use the Redding body dies to full length size when needed I don't see it slowing me down anyway...

 

[TresMon]

Re: Neck Tension Question


So what is the magic procedure to get the force equalized?

 

[Hummer]

Re: Neck Tension Question

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TresMon</div><div class="ubbcode-body">
So what is the magic procedure to get the force equalized? </div></div>

Congratulations you have just asked the $1,000,000.00 question.

Small case volume seems to have much to do with it thus the 6BR shoots so well. My buddy with no problem got SDs like 3 and 4 on his with groups under an inch at 300 yards from his Grunig which if I was in the "I don't care what it costs club" I would be getting. They have a much superior design IMHO to what is seen here.

He loaded his ammo on my equipment and scales and his SDs were amazing. He said the Norma 6BR ammo was so good that many of the 300 meter shooters in Europe gave up reloading and just buy new. He brought over two cases of 50 round boxes of once fired empty brass about ten years ago and sold the brass here.

He was one great guy with lots of good info but the Brit healthcare (joke) allowed him to die at 67.