Measuring neck tension

[Willie]

Some of us know that, of the 3 components of the Holy Trinity of precision ammo (powder, seating depth and neck tension), neck tension is the most difficult to control.

I know that everyone likes to control neck tension with bushings but to me that doesn't seem like a very good way. From my way of thinking bushings transfer any variance in neck thickness to the inside of the neck where they have a direct impact on neck tension. That is not a good thing, because no matter how careful you are turning necks there will be variances, and those variances will impact neck tension.

I believe that the outside of the neck has minimal importance, as long as there is a minimum .003 neck clearance for bullet release. The only important thing is how thick the necks are because that has an influence on spring-back. IMO the part of the neck everyone should be focusing on is the inside of the neck, or more appropriately inside diameter. The inside diameter is what influences neck tension, if one can transfer neck wall variances to the outside of the case it is that much better.

So the question is: How do we control neck tension from the inside of the neck? What if instead of honing die necks (an irreversible and often problematic process because dies are hardened, not to mention that you have to be twice as accurate with a die then with a mandrel, an impossible taskfor most small machine shops) we were to use a mandrel to expand the necks to provide the desired neck tension? What would a mandrel do?

Well, ... a mandrel would control the inside diameter of a case neck much more precisely than any bushing ever can. It could also transfer neck thickness variances to the outside of the neck where it doesn't interfere with neck tension and bullet release. That's good isn't it?

I have been using mandrels for thousands of cases. The problem is that just when I have a mandrel that gives ideal neck tension (down to .0001 precision) it starts to wear, and after a couple of thousand cases it is done. Making another mandrel to .0001 precision is very difficult/not possible for most machine shops and grinding shops. So I set out to look for a solution. I eventually focused on the Hornady bullet puller collet, because that's what I had. I started using the bullet puller to hold pin gages to expand the necks to match the turner mandrel.

However, the bullet puller did not hold the pin gages as co-axially straight as I wanted, so I approached Kenny Porter ( kennethp@portersprecisionproducts.com ), who makes all kinds of things including parts for pacemakers (can you think of anything more critical?). I told him I wanted him to make a die for me that would hold a pin gage, actually a range of pin gages ie .305, .306, .307, .308 and .309. Once I showed him what I had in mind he made a leap to a collet that is ideally suited for what I wanted. The collet holds the cutting bit for a CNC machine. It has real holding power. Here’ the mandrel die that Kenny Porter made for me.

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Pin gages are small tubes 2" long and can be bought for a few dollars and they are available in dimensions as exact as .0001 (+/- .00002). They generally have a 60 to 62 Rockwell hardness, like tool steel. They are ideal for this purpose, all you have to do is bevel the tip. To bevel the tip all I do is chuck the mandrel in a drill and spin it against a grinding stone until I get the tip that I desire. Takes less than 5 minutes.


Now, when I need a new mandrel I buy a Vermont Gage pin gauge. If you’re looking for +/- .0002 precision they are round $3 each. If you really want to get precise and have a mandrel to .0001 (+/- .00002) precision then the price jumps to around $18 and you’ll have to order directly from Vermont Gage. For $18 you get a mandrel and a certificate of accuracy and the name of the guy that inspected and when.

This mandrel die makes all other mandrel die I have seen or bought look primitive.

Joe

P.S. I use this die in conjuction with the 21st Century Hydro press to achieve consistent measurement of seating force.

Joe, you sold me on this last year. I set up with collets to handle a range of calibers and have excellent results. I only wish I could grind more consistent tapers on the pin gauges. I have been practicing, but have a long way to go. HaHa!

 

[Campbell]

Will the tension force gripping the bullet be the same for all neck wall thickness and hardness?

The linked article on neck tension in post #2 finishes with:


It is easy to measure the force needed to get the bullet out of the case neck. It is far from being a phenomenon and simple to quantify.

No! But neck tension measured by the aforesaid method has to be a convenient starting point?

 

[Campbell]

Some of us know that, of the 3 components of the Holy Trinity of precision ammo (powder, seating depth and neck tension), neck tension is the most difficult to control.

I know that everyone likes to control neck tension with bushings but to me that doesn't seem like a very good way. From my way of thinking bushings transfer any variance in neck thickness to the inside of the neck where they have a direct impact on neck tension. That is not a good thing, because no matter how careful you are turning necks there will be variances, and those variances will impact neck tension.

I believe that the outside of the neck has minimal importance, as long as there is a minimum .003 neck clearance for bullet release. The only important thing is how thick the necks are because that has an influence on spring-back. IMO the part of the neck everyone should be focusing on is the inside of the neck, or more appropriately inside diameter. The inside diameter is what influences neck tension, if one can transfer neck wall variances to the outside of the case it is that much better.

So the question is: How do we control neck tension from the inside of the neck? What if instead of honing die necks (an irreversible and often problematic process because dies are hardened, not to mention that you have to be twice as accurate with a die then with a mandrel, an impossible taskfor most small machine shops) we were to use a mandrel to expand the necks to provide the desired neck tension? What would a mandrel do?

Well, ... a mandrel would control the inside diameter of a case neck much more precisely than any bushing ever can. It could also transfer neck thickness variances to the outside of the neck where it doesn't interfere with neck tension and bullet release. That's good isn't it?

I have been using mandrels for thousands of cases. The problem is that just when I have a mandrel that gives ideal neck tension (down to .0001 precision) it starts to wear, and after a couple of thousand cases it is done. Making another mandrel to .0001 precision is very difficult/not possible for most machine shops and grinding shops. So I set out to look for a solution. I eventually focused on the Hornady bullet puller collet, because that's what I had. I started using the bullet puller to hold pin gages to expand the necks to match the turner mandrel.

However, the bullet puller did not hold the pin gages as co-axially straight as I wanted, so I approached Kenny Porter ( kennethp@portersprecisionproducts.com ), who makes all kinds of things including parts for pacemakers (can you think of anything more critical?). I told him I wanted him to make a die for me that would hold a pin gage, actually a range of pin gages ie .305, .306, .307, .308 and .309. Once I showed him what I had in mind he made a leap to a collet that is ideally suited for what I wanted. The collet holds the cutting bit for a CNC machine. It has real holding power. Here’ the mandrel die that Kenny Porter made for me.

View attachment 1033999

View attachment 1034000

View attachment 1034001

View attachment 1034002

Pin gages are small tubes 2" long and can be bought for a few dollars and they are available in dimensions as exact as .0001 (+/- .00002). They generally have a 60 to 62 Rockwell hardness, like tool steel. They are ideal for this purpose, all you have to do is bevel the tip. To bevel the tip all I do is chuck the mandrel in a drill and spin it against a grinding stone until I get the tip that I desire. Takes less than 5 minutes.


Now, when I need a new mandrel I buy a Vermont Gage pin gauge. If you’re looking for +/- .0002 precision they are round $3 each. If you really want to get precise and have a mandrel to .0001 (+/- .00002) precision then the price jumps to around $18 and you’ll have to order directly from Vermont Gage. For $18 you get a mandrel and a certificate of accuracy and the name of the guy that inspected and when.

This mandrel die makes all other mandrel die I have seen or bought look primitive.

Joe

P.S. I use this die in conjuction with the 21st Century Hydro press to achieve consistent measurement of seating force.

Many thanks for this Joe!

I will have to take time to digest this superb post.

Cam

 

[Bart B.]

No! But neck tension measured by the aforesaid method has to be a convenient starting point?

Yes, but only if bullet pull force is measured to see the pounds required. A .0005" interference fit may need 6 pounds with one lot of cases but 10 pounds with another lot with thicker neck walls. .

 

[BenPerfected]

Another option is K&M. They offer a mandrel kit in .0005 increments.
Ben

 

[Campbell]

Yes, but only if bullet pull force is measured to see the pounds required. A .0005" interference fit may need 6 pounds with one lot of cases but 10 pounds with another lot with thicker neck walls. .

IMO the actual force to move the bullet is irrelevant given that the psi is in the region of 55-60k. What is relevant, IMO, is the consistency of the neck "tension"

 

[BenPerfected]

IMO the actual force to move the bullet is irrelevant given that the psi is in the region of 55-60k. What is relevant, IMO, is the consistency of the neck "tension"

Would the bullet move before the neck expands?

 

[muleman69]

Some of us know that, of the 3 components of the Holy Trinity of precision ammo (powder, seating depth and neck tension), neck tension is the most difficult to control.

I know that everyone likes to control neck tension with bushings but to me that doesn't seem like a very good way. From my way of thinking bushings transfer any variance in neck thickness to the inside of the neck where they have a direct impact on neck tension. That is not a good thing, because no matter how careful you are turning necks there will be variances, and those variances will impact neck tension.

I believe that the outside of the neck has minimal importance, as long as there is a minimum .003 neck clearance for bullet release. The only important thing is how thick the necks are because that has an influence on spring-back. IMO the part of the neck everyone should be focusing on is the inside of the neck, or more appropriately inside diameter. The inside diameter is what influences neck tension, if one can transfer neck wall variances to the outside of the case it is that much better.

So the question is: How do we control neck tension from the inside of the neck? What if instead of honing die necks (an irreversible and often problematic process because dies are hardened, not to mention that you have to be twice as accurate with a die then with a mandrel, an impossible taskfor most small machine shops) we were to use a mandrel to expand the necks to provide the desired neck tension? What would a mandrel do?

Well, ... a mandrel would control the inside diameter of a case neck much more precisely than any bushing ever can. It could also transfer neck thickness variances to the outside of the neck where it doesn't interfere with neck tension and bullet release. That's good isn't it?

I have been using mandrels for thousands of cases. The problem is that just when I have a mandrel that gives ideal neck tension (down to .0001 precision) it starts to wear, and after a couple of thousand cases it is done. Making another mandrel to .0001 precision is very difficult/not possible for most machine shops and grinding shops. So I set out to look for a solution. I eventually focused on the Hornady bullet puller collet, because that's what I had. I started using the bullet puller to hold pin gages to expand the necks to match the turner mandrel.

However, the bullet puller did not hold the pin gages as co-axially straight as I wanted, so I approached Kenny Porter ( kennethp@portersprecisionproducts.com ), who makes all kinds of things including parts for pacemakers (can you think of anything more critical?). I told him I wanted him to make a die for me that would hold a pin gage, actually a range of pin gages ie .305, .306, .307, .308 and .309. Once I showed him what I had in mind he made a leap to a collet that is ideally suited for what I wanted. The collet holds the cutting bit for a CNC machine. It has real holding power. Here’ the mandrel die that Kenny Porter made for me.
I really like this tool,so would there be any reason to turn the necks (any benefits) I'm running 30 cal so what mandrel would you suggest ?
View attachment 1033999

View attachment 1034000

View attachment 1034001

View attachment 1034002

Pin gages are small tubes 2" long and can be bought for a few dollars and they are available in dimensions as exact as .0001 (+/- .00002). They generally have a 60 to 62 Rockwell hardness, like tool steel. They are ideal for this purpose, all you have to do is bevel the tip. To bevel the tip all I do is chuck the mandrel in a drill and spin it against a grinding stone until I get the tip that I desire. Takes less than 5 minutes.


Now, when I need a new mandrel I buy a Vermont Gage pin gauge. If you’re looking for +/- .0002 precision they are round $3 each. If you really want to get precise and have a mandrel to .0001 (+/- .00002) precision then the price jumps to around $18 and you’ll have to order directly from Vermont Gage. For $18 you get a mandrel and a certificate of accuracy and the name of the guy that inspected and when.

This mandrel die makes all other mandrel die I have seen or bought look primitive.

Joe

P.S. I use this die in conjuction with the 21st Century Hydro press to achieve consistent measurement of seating force.

 

[muleman69]

Joe R,I kind of messed up my reply as it got stuck inside your post. I really like your invention and was asking if there was any reason for neck turning at all? I shoot .30 cal. and was wondering what size of mandrel you would suggest me getting?

 

[Bart B.]

Would the bullet move before the neck expands?

Yes. If the bullet needs only 5 pounds of force to move it forward in the case neck, that happens when pressure in the 30 caliber case is only 67 psi. If 10 pounds, at 134 psi.

Formula is bullet cross section in square inches (about .0745 square inches for 30 caliber bullets) times psi to equal 5 pounds of force on the bullet. 67 X .0745 = 5 pounds. 100 psi puts 1 pound of pressure on each one-tenth square inch of area. Reciprocal of .0745 is 13.42, that times 5 is 67.1

Bullet's are a few inches down the bore at peak pressure.


Aw, shucks. Used 22 caliber bore diameter instead of .224 bullet diameter. Give me 2 demerits.

7.62 NATO service ammo bullet release force is a minimum of 60 pounds. What psi level starts those bullets to move in the case neck? What about M118LR with a minimum of 20 pounds?

 

[Campbell]

I suppose (?) that the acid test for consistent neck tension (every thing else being equal) is MV. My MV spread is 6 fps at an average of 2421

 

[BenPerfected]

Been down this road. Paid Roger $27 plus shipping for a custom mandrel that was .0012 off my requested size. Than he tries to tell me that I must have dropped my micrometer and its not accurate as his. And when I told him that I can check its accuracy using feeler gages or pin gages he hung up on me. Actually he was the motivating force for me to get off my duff and come up with a universal solution that actually works, so he and people like him could stop swindling shooters.
SHV 4-14x56

Joe, my experience was the opposite of yours with K&M. Roger spent close to an hour on the phone with me helping me really understand the importance of expander mandrels in .0005 increments and the relationship of expanding necks, neck “tension” and annealing. I asked a min of 20 questions over about 45 min conversation and would say his knowledge of managing brass is in the same category as Darrell Jones.
Ben



Muleman69,
At $3 a each I would suggest that you get pin .305-.308 pin gages I also think a .310 pin gage is handy to have when you drop a case on concrete and and the mouth gets dented. I also use it to set the tension on my Hornady OAL gage case.

Here's the link https://www.amazon.com/dp/B004THCBEI/?tag=accuratescom-20

Regards,

Joe

View attachment 1034135

 

[muleman69]

This good stuff,I will look them up on amazon. So were do I order the die ? I could not open the link from above. Tks

 

[Campbell]

Whoa!!!
Cam,
If you can consistently get single digit ESs in a 5 or 10 shot group and good precision, you are golden. Don't waste your time talking to dorks like me. Post some targets with numbers so we can all drool over them.

Joe

P.S. What kind of shooting you doing and bullets are you using that you get 2421 fps?

Hi Joe

I was using a Parker Hale 1200TX doing what we call in our club "Factory Sporter". The course of fire is 300, 500, 600 and occasionally 1000 yards. My best 2 scores at 600 yards totalled 199.30/200.40 and have won the 600 yard Factory Sporter which I am chuffed about. I have also shot against the F/TR boys and girls, but, as you can imagine, my performance is a lot less dazzling (especially considering that there a 6 Team GB members in the club). The club is the 101 Rifle club based at Altcar, Merseyside.

I am using 155gr HBC Projectiles with 46gr of Vit 140. I use a tuned RCBS 5.0.5 with a 20x zoom camera looking at an extended needle pointer. A single kernel of powder is easily detectable, and I attribute the low spread down to the accuracy of charge weight. One of the team GB members has got his even lower!!!

 

[PatMiles]

I bought one of Kenny Porter's collet dies about a year ago after trading PMs with Joe. It works perfectly.
As Joe mentioned, different size pin gages will fit the collet, within a certain range, so you can experiment neck expansion for different neck tension.
One other big bonus with Kenny's die is the fact that it takes ER16 collets so if you want to play with neck expansion for another caliber you simply buy an ER 16 collet that accepts the range of pin gages you will need for the additional caliber. I ordered Kennys die with a collet that would accept the pins around .264" for my 6.5 Creedmoor. Later I bought a collet on Ebay that fit the pins for my 6PPC gun, .243", the same collet will take pins for my .223" gun. If you decide to go this route, buy good quality ER16 collets as you are chasing accuracy.
Here is a bit of info for ER16 collets, as you can see, each collet in the calibers we shoot has a range of .039" of pins. Very versatile.


ER16 series collets have a capacity of .015-.4375 inches. Each ER16 collet has a range of .039 inches(1mm). ER16 Collets .118 and smaller have a range of only .015 inches. The size indicated on the collet is the largest size it can hold and can be collapsed smaller within its collapse range mentioned above.

 

[muleman69]

I don't know why you can't open the link it works for me. But you can just search Amazon for " Vermont Gage pin gages". Here's the link to KennY Porter, the man that made that die for me: http://www.portersprecisionproducts.com

Mine was a prototype so it costs me nearly 3 times what he selling them now for, but it was worth it to me. I'm not really sure what the exact price is you'll have to email him and ask.

Good luck,

Joe

Okay thanks I found it now

 

[Bart B.]

I suppose (?) that the acid test for consistent neck tension (every thing else being equal) is MV. My MV spread is 6 fps at an average of 2421

Here's my opinions..... But a 6 fps MV spread is great!!

Acid test for necks gripping bullets is measuring bullet release force.

Muzzle velocity tests with shouldered rifles get bigger ES and SD numbers. Free recoiling rifles are better, but not as good as fixed barreled actions. Velocity tests evaluate primer and powder and are best done after bullet release force spread is minimized

 

[Campbell]

hHere's my opinions..... But a 6 fps MV spread is great!!

Acid test for necks gripping bullets is measuring bullet release force.

Muzzle velocity tests with shouldered rifles get bigger ES and SD numbers. Free recoiling rifles are better, but not as good as fixed barreled actions. Velocity tests evaluate primer and powder and are best done after bullet release force spread is minimized

What I love about this forum is that one can learn something new every day about stuff that initially seems so basic!

Later this week I will study your argument! Please bare with me and thanks!

 

[Hanbleceya]

The industry standard (SAAMI) is the force needed to push or pull a bullet from the case neck. Military specs use extraction force. This is what the burning powder has to overcome. 7.62 and 5.56 service ammo has 45 to 60 pounds extraction forces. 7.62 match ammo, 20 pounds minimum. Ive used a couple to about 15 pounds pulling bullets from inverted cases weighing the collet bullet puller and bags of bullets attached. I think this gives a better measurement than diameter differences

A given interference fit (diameter difference) will have different forces needed due to metal hardness and friction.

That said, a .0005" interference fit may be good. I've used less. Die necks .001" to .002" smaller than loaded round necks usually works. There's a bit of case neck springback. The case neck springs back a few ten-thousandths from the sized diameter.

1-2 made a big difference early on for me. When I did this, I felt the difference when seating the bullet, went to the range, and observed a significant difference.

Useful information.

 

[Olde Man]

The info provided in this post is very useful to me as I have been struggling with seating pressure, neck tension and resulting ES. My main concern is that I can observe the seating pressure required and then cull the highs and lows. Do you think that if you used the selected mandrel to size the neck on the first pass and then insert the mandrel again observing the pressure required that the result would be a number that would be representative all of the case related variables. This should only leave things like bullet related variables. I find that once I have assembled a bullet and find it is out of my range that if I take it apart a couple of times that I have to shoot it to make the case usable again. What a waste.