Arbor press and pressure

[misser]

i also use the 21st Century hydro press . it does show things you other wise would not know. when loading for the AR 15 223 i like 60-80 psi on the diel .mostly because of the inertia thats induced and then that sudden stop of the cartridge. bullets would like to keep moving forward . moving bullets just a few thousands can and will impact target differently . been there done that. its more of a problem with AR10's 30's(308) .

so i know how much psi is being used to push the bullet in .then to know how much pressure is needed to move the bullet back out?? i dont know that number

 

[Chaotik]

Once you've formed brass to stable, and load developed with that, and figured out that you need to leave carbon residue in the necks(normalizing friction), then you can correlate tension departures in a batch.
That won't do you any good with bullets already seated to see it.
But you can set offenders aside, and eventually see when it's time to reset the whole batch with a process anneal.

I use a different system where I measure pre-seating forces with an instrumented mandrel, and then adjust tension through neck sizing length to match all in batch. This, before any bullet seating.

@mikecr Could you explain your different system with an instrumented mandrel? As far as I know, there is no commercially available method to measure actual neck tension or the grip of the case neck on the bullet. And what we look at when we seat the bullet is friction, at best very indirectly related to neck tension. And once the primer ignites the powder and the case and case neck expand (before the bullet begins to move), friction in the neck has no influence on the results on the target.
But I could be wrong....

 

[Wild Bill IV]

@mikecr Could you explain your different system with an instrumented mandrel? As far as I know, there is no commercially available method to measure actual neck tension or the grip of the case neck on the bullet. And what we look at when we seat the bullet is friction, at best very indirectly related to neck tension. And once the primer ignites the powder and the case and case neck expand (before the bullet begins to move), friction in the neck has no influence on the results on the target.
But I could be wrong....

The bullet is held in place by Static (stationary by slight adhesion from tension) friction (pressure) which require more force (pressure) than the kinetic (sliding) friction!! Tension is a component of friction!! Fiction=the coefficient of friction of two sliding surfaces x the tension!!!

That bullet does not magically (voodoo) hang in the chamber unsupported!!! The bullet is shoved into the rifling long before the pressure blows out (rolls) the neck!!! Before the bullets moves, the gas pressure vectors are pointed outward in all direction shoving the bullet forward after it exceeds the Static frictional force!! Since the bullet is still in the neck, there is no gas pressure on the neck and it keeps it form!! As that bullet moves forward, it exposing more and more of the neck to the gas pressure!!! The neck rolls outward and very lightly forward as more and more of the neck is exposed to the gas pressure vectors!! The biggest flaw in the shooting sports lingo is "BRASS FLOWS"!!! It only flows in the hot molten liquid state!!! No, The brass is roll formed outward by gas pressure just like the pressure (force of the press) of the forming dies roll forms the brass back inward!!!

Think of the measurement units!!!
POUNDS PER SQUARE INCH!! An exponential formula (power factor of 2) when grafted will have a curve form!!! If it was pounds per inch, the graft would be linear!!!
If the bullet is occupying all of inside neck area, there is no pressure on/in the neck from building gases!!! As the bullet slides forward, it allows increasing inside neck area to be exposed too the building gas pressure!!! When the gas pressure reaches brass deformation pressure, the brass blows out!! A little more pressure will shove the bullet down the barrel after it exceeds bullet deformation (cutting and deformation from the rifling) pressure!!! At this point, bullet/rifle friction is so small compared to the near peak chamber pressure that the bullet undergoes extreme acceleration.
WHAT IS THE MAXIMUM FORCE ACTING ON THAT BULLET???
MAX FORCE=PEAK PRESSURE x CALIBER AREA!!!

Static friction can be measured!!! But it requires shoving the bullet deeper into the case!!! By making the seating depth deeper, theses presses can apply pressure to the seated round and record the peak pressure to make the bullet move!!! That peak pressure is the breaking point of the static friction of the neck tension/bullet compression equalized forces!!!

The competitor looking for an advantage should be looking at the uniformity of static friction and where the bullet break away pressure position is in the total pressure curve of the powder burn!! It is the largest force, other than bullet deformation caused by the rifling, when looking at bullet release from the neck!! And, once that bullet is released, kinetic friction plays less (but still important) of an effect in the internal dynamics!!! Tension is not solely the Holy Grail of case neck/bullet dynamics!! Holding a consistent coefficient of friction is just as important!!!

This is why I ream the necks!!! Most of the dynamics is on the inside of the case!!! I can control tension and coefficients of friction by reaming and trim case length to equalize inside neck area with one case prep operation!!! Look at the 10x picture of the cutaway of the neck in a 6.5PRC!!! The darker lines are recessed micro grooves!!! They act as air bearings thus reducing the coefficient of friction!!! It also reduces surface contact of the bullet!!! Less surface area, even less friction!!! It requires greater pressure to break the Static friction since it is a ribbed contact on the cylinder of the bullet!!! This will move the breaking pressure closer to the brass and bullet deformation pressures!! Hand reaming is a cold shearing operation!!! No heat is detected by touch!!! No heat, no added stress and strain forces, very little work hardening of the brass if any, and more consistent tension!!! Yeah, I'm using the same neck bushing for reforming the neck after firing that I used for forming the outside of the neck prior to reaming!!! The reamers is 0.263" which sets the neck tension!!! And it is a straight true cut!! Don't need the expander or use a mandrel before bullet seating!!! Will be testing bare cleaned necks vs carbon buildup necks after fine tuning my loads!!

 

[mikecr]

@mikecrAs far as I know, there is no commercially available method to measure actual neck tension or the grip of the case neck on the bullet. And what we look at when we seat the bullet is friction, at best very indirectly related to neck tension.

You are correct.
We have no way to measure tension right now.
Seating force and tension are separate and different.
By normalizing friction, which a carbon layer does, we can see tension variances using seating or pre-seating forces.

@mikecrAnd once the primer ignites the powder and the case and case neck expand (before the bullet begins to move), friction in the neck has no influence on the results on the target.

Correct also.
Bullets are normally neck released based on tension, regardless of dry neck friction.

I use a Sinclair mandrel die with a button load cell above the mandrel, that the mandrel raises against.

 

[Wild Bill IV]

You are correct.
We have no way to measure tension right now.
Seating force and tension are separate and different.
By normalizing friction, which a carbon layer does, we can see tension variances using seating or pre-seating forces.

Correct also.
Bullets are normally neck released based on tension, regardless of dry neck friction.

I use a Sinclair mandrel die with a button load cell above the mandrel, that the mandrel raises against.
View attachment 1560310

SF (static friction) = CSf x Weight
Kf (kinetic friction) = CKf x Weight
Tension = Weight from Fig 1 in attachment
If your load cell reads 120lbs max at seating, you are measuring the Kf (kinetic friction force)! Therefore, The Tension force of the neck = 120lbs ÷ 1.0 (copper on copper kinetic frictional coeffient)!!!
The neck tension is 120 lbs!!!!
To break the static friction force (bullet release force) of the equalized state of opposing forces (bullet compression = neck tension in figure 2 in attachment) you need 120lbs (tension) x 1.6 (copper on copper static frictional coefficient) = 192 lbs of force!!! As you can see, static friction is much greater than kinetic friction!!
You have the tools to measure Neck Tension and need to use mathematics and physics to find that values!!! The biggest problem is finding the coefficients of static and kinetic friction of copper on carbon!!

You have the tools, just need to find or test to find the factorial constants!!! Let's ball park this issue and use Mark's (quest450) curves on bare brass vs 6x fired carbon coated neck curves!!! Using 1 for copper on copper KCOf at around 130lbs and 6x at around 40lbs!! Without true data and stats, THIS IS BALL PARK CALCULATIONS AND ASSUMPTIONS!!! I did a rough ratio calc of .308 for K copper on carbon!!! Lets look at around his 40lb seating force!!! Mark's tension is around 40lbs/.308 = 130lbs!! Very close to the 120lbs from the 1st calc above!! Well within 10% error!!! DOES THE CARBON INCREASE THE TENSION???? Or is my guess off!! His static friction would be (Ratio assumed value for SCOf) is 0.5!!! Very close since carbon has a lot more surface area than brass!! Marks assumed by double ratio best guesses static friction is 230lbs!!

Using Mark's static friction solution of 230lb, we can find the pressure required to release that bullet using the formula
P (pressure to release the bullet) = Force (Static friction) ÷ A (area of base face of the bullet)!!
P = 230 ÷ ((caliber/4)squared x π)
For a 6.5 bullet, the bullet release pressure is 16,807psi on the base of the bullet!! Let's look at its position on the chamber pressure curve with a peak pressure of 55,000psi!! It is 30.6% or just a little under the 1/3th up from the very start of up sloping pressure curve!!!

Does the neck expand before the bullet is released??
Let's assume a neck thickness of 12 thou and minimal neck camber bore clearance of 3 thou!!! The OD of neck for a 6.5 would be .288 with a neck chamber bore of .291!! The area in question is the neck chamber bore area - neck OD area!!
0.133 sqin - 0.130 sqin = 0.003 sqin
The force on that area when the bullet is released is 16,807psi x 0.003 sqin = 50lbs!!
The neck tension is 4.6 times greater than the pressure force on this region in question!!! The neck keeps its bullet seating form at bullet release pressures!! This is why there are carbon deposits on the outside of the neck after firing due to the turbulent flow of the remain gases exhausting before the neck is expanded by the higher pressures following bullet release!!

I have worked with engineering and physics for over 45 years!! Performed consulting engineering solutions (will working for Connelly & Associates) at Swift Bullet in Quinter, KS on lead core extrusion thermal problems and hazardous exhaust air capture system component changes to exceed new EPA air emissions standards and limits in their ballistic tunnel!! Most of the problems on forums are really easy and common problems from day to day at work!!! Retired now and want to pass my knowledge and experiences with form members to improve their knowledge and experience in shooting sports!!! With 105 credit hours of applied science courses, I can say, I KNOW A LITTLE OF EVERYTHING, AND A LOT OF NOTHING!!!

Aim Small, Hit Big!!!
BILL

I just realized your load cell is on a mandrel!! If you could get a gliden copper mandrel of exact bullet diameter you could measure the static friction force directly!!! Seat the copper mandrel after Sinclair mandrel forming, where the chamfer/main shaft is a hair below the neck/shoulder junction! Let it rest for a minute or two to allow compression and tension equalization!!! Then watch the meter for peak static break as you slowly add more downward force on the copper mandrel!!! That is the same force of the bullet release!!! You have the right tool, just need a copper mandrel for testing!! But, you have to reform and Sinclair mandrel on all tested brass!!!

 

[mikecr]

What grips our bullets/delays release during firing is hoop tension (not friction).
That gripping force is tied to cal diameter, brass thickness, brass hardness, stress-strain curve setting, and area of force applied. It's unit of measure (if we measured it) would be in PSI.

I can set hoop tension to anything regardless of friction (which I can also set to anything).
They are separate different things.
My instrumented mandrel DOES NOT measure tension,, and nothing on the market does.
Measuring hoop tension would require measure of expansion force per displacement (while expanding) to generate and set position on a stress-strain curve for each neck. If it were easy, we'd all have it.

 

[Bob3700]

The bullet is held in place by Static (stationary by slight adhesion from tension) friction (pressure) which require more force (pressure) than the kinetic (sliding) friction!! Tension is a component of friction!! Fiction=the coefficient of friction of two sliding surfaces x the tension!!!

That bullet does not magically (voodoo) hang in the chamber unsupported!!! The bullet is shoved into the rifling long before the pressure blows out (rolls) the neck!!! Before the bullets moves, the gas pressure vectors are pointed outward in all direction shoving the bullet forward after it exceeds the Static frictional force!! Since the bullet is still in the neck, there is no gas pressure on the neck and it keeps it form!! As that bullet moves forward, it exposing more and more of the neck to the gas pressure!!! The neck rolls outward and very lightly forward as more and more of the neck is exposed to the gas pressure vectors!! The biggest flaw in the shooting sports lingo is "BRASS FLOWS"!!! It only flows in the hot molten liquid state!!! No, The brass is roll formed outward by gas pressure just like the pressure (force of the press) of the forming dies roll forms the brass back inward!!!

Think of the measurement units!!!
POUNDS PER SQUARE INCH!! An exponential formula (power factor of 2) when grafted will have a curve form!!! If it was pounds per inch, the graft would be linear!!!
If the bullet is occupying all of inside neck area, there is no pressure on/in the neck from building gases!!! As the bullet slides forward, it allows increasing inside neck area to be exposed too the building gas pressure!!! When the gas pressure reaches brass deformation pressure, the brass blows out!! A little more pressure will shove the bullet down the barrel after it exceeds bullet deformation (cutting and deformation from the rifling) pressure!!! At this point, bullet/rifle friction is so small compared to the near peak chamber pressure that the bullet undergoes extreme acceleration.
WHAT IS THE MAXIMUM FORCE ACTING ON THAT BULLET???
MAX FORCE=PEAK PRESSURE x CALIBER AREA!!!

Static friction can be measured!!! But it requires shoving the bullet deeper into the case!!! By making the seating depth deeper, theses presses can apply pressure to the seated round and record the peak pressure to make the bullet move!!! That peak pressure is the breaking point of the static friction of the neck tension/bullet compression equalized forces!!!

The competitor looking for an advantage should be looking at the uniformity of static friction and where the bullet break away pressure position is in the total pressure curve of the powder burn!! It is the largest force, other than bullet deformation caused by the rifling, when looking at bullet release from the neck!! And, once that bullet is released, kinetic friction plays less (but still important) of an effect in the internal dynamics!!! Tension is not solely the Holy Grail of case neck/bullet dynamics!! Holding a consistent coefficient of friction is just as important!!!

This is why I ream the necks!!! Most of the dynamics is on the inside of the case!!! I can control tension and coefficients of friction by reaming and trim case length to equalize inside neck area with one case prep operation!!! Look at the 10x picture of the cutaway of the neck in a 6.5PRC!!! The darker lines are recessed micro grooves!!! They act as air bearings thus reducing the coefficient of friction!!! It also reduces surface contact of the bullet!!! Less surface area, even less friction!!! It requires greater pressure to break the Static friction since it is a ribbed contact on the cylinder of the bullet!!! This will move the breaking pressure closer to the brass and bullet deformation pressures!! Hand reaming is a cold shearing operation!!! No heat is detected by touch!!! No heat, no added stress and strain forces, very little work hardening of the brass if any, and more consistent tension!!! Yeah, I'm using the same neck bushing for reforming the neck after firing that I used for forming the outside of the neck prior to reaming!!! The reamers is 0.263" which sets the neck tension!!! And it is a straight true cut!! Don't need the expander or use a mandrel before bullet seating!!! Will be testing bare cleaned necks vs carbon buildup necks after fine tuning my loads!!

WB,
I have to agree with you 100% on the inside neck reaming. My brass is inside, inline neck reamed. The case is held in a FL sizing die (custom die I made) and a reamer is run in from the top to establish the ID of the neck. The reamer cuts the neck true to the centerline of the case. This, I believe, also helps start the bullet straighter down the bore during firing.
Outside neck turning always seemed to me to keep any neck variations to the inside of the case. Yes you turned the outside round, but the mandrel is riding on the high spots of the brass.
With inside reaming, you also keep up on any brass flowing forward at the base of the neck. I don't seat my bullets that deep anyway, but I can see the reamer cutting the donuts away after a few firings.

 

[Wild Bill IV]

WB,
I have to agree with you 100% on the inside neck reaming. My brass is inside, inline neck reamed. The case is held in a FL sizing die (custom die I made) and a reamer is run in from the top to establish the ID of the neck. The reamer cuts the neck true to the centerline of the case. This, I believe, also helps start the bullet straighter down the bore during firing.
Outside neck turning always seemed to me to keep any neck variations to the inside of the case. Yes you turned the outside round, but the mandrel is riding on the high spots of the brass.
With inside reaming, you also keep up on any brass flowing forward at the base of the neck. I don't seat my bullets that deep anyway, but I can see the reamer cutting the donuts away after a few firings.

Are we the only two that enjoy that straight, clean cut neck that is accurate!!! I gave my son a complete benchrest hand die kit for 223 made in the 70s!!! It too had a die where you soft tap the case in and had a reamer that fit in the hand tap seating bushing!!! Micrometer outside adjustment!!! That made really accurate loads!!!

 

[Wild Bill IV]

What grips our bullets/delays release during firing is hoop tension (not friction).
That gripping force is tied to cal diameter, brass thickness, brass hardness, stress-strain curve setting, and area of force applied. It's unit of measure (if we measured it) would be in PSI. This is one of the hardest concepts of physics!! It just doesn't make sense until you think density and distribution!!! After doing the assigned problems, the concept came to light!! It is hard to grasp, but trust the science, it works!!

I can set hoop tension to anything regardless of friction (which I can also set to anything).
They are separate different things.
My instrumented mandrel DOES NOT measure tension,, and nothing on the market does.
Measuring hoop tension would require measure of expansion force per displacement (while expanding) to generate and set position on a stress-strain curve for each neck. If it were easy, we'd all have it.

DID YOU LOOK AT THE ATTACHMENT???
THAT IS THE DIAGRAM FOR TESTING TENSION!!! DID YOU LOOK AT THE LETTER HEAD???

Fiction, tension, compression, weight, drag, stress, strain, bending, shearing, etc are all derived forces from Newton's 2nd law of changing momentum (acceleration) which yield the general formula, F=ma, and the interaction of forces (action/reaction at rest or in motion) and the units are Newtons or Pounds!! Not psi!! The reason we don't use unit areas for friction, tension, and compression is described in the attachment! This is from the fundamentals of physics, not the advanced!! Note the orientations in Fig 6.31!! Read the 1st indented paragraph!!

Think of a rubber band slipped over a cylinder!! The rubber band has tension (ACTION) pointing inward towards the center!! That stretched rubber band is trying to move inward, towards the center, relieving the stretch and regaining it's original form!! The cylinder is holding the rubber band outward and that force is compression (REACTION) pushing out from center!!! In the rest state, it is static and the 2 forces (TENSION/ACTION, COMPRESSION/REACTION) are equal!! Studied Statics (3 hr) where steel truss problems were solved by either compression, compression, tension, CCT or tension, tension, compression TTC force triangles!!! Rigid bodies can undergo both compression or tension!!!

Engineering fit specifications (shafts, bearings, pulleys, sheaves, bushings, couplers, sprockets, gears, etc) are based on tension and compression just like the bullet to neck fit!!!

You can not change the tension without changing the form or induce unwanted internal forces!! Tempering, work hardening, grain size shrinkage, stress, and strain which are all unwanted thermodynamics properties (advanced physics)!!! But, you can have more uniformity, consistency by keeping necks thick!! Tension and compression for brass can only move the brass 0.0005" max!!! That is the recoil (reaction) of the loading forces!! Anything more is deformation!! That is engineered into the design of dies and expanders! Just like expansion and contraction (thermodynamics properties) of the two different metals in the chamber allow extraction of the case out chamber!! That terminology is based on bi-metals used in thermostats, circuit breakers, GFI, etc!!!!

But, your press can measure the tension, and the static friction with mathematics!!! You have the potential advantage over other shooter, if you choose to use the math as a tool and let a retired engineer teach you how to use those tools and make them work for YOU!!!

 

[mikecr]

Bullets are not pushed from necks on firing, so neck friction is meaningless to internal ballistics.
Instead, bullets are released, with even a billionth of an inch of neck expansion from bullet bearing.

You can increase friction, like with squeaky clean bullets and neck IDs, and it will not affect MV or pressure one bit. You can decrease friction of bullets and neck IDs with WS2, and again, no affect to firing results.
But if you change neck tension either way, you get direct results.

Tension being spring back grip in PSI, can be adjusted through area of force applied to bullet bearing.
Easily accomplished through neck sizing length adjustments.
And of course you can adjust tension with brass hardness, which is again independent of friction.

 

[jsthntn247]

Yes, there is but there are other factors friction related that show up more. So a bushing change will show up, but its small compared to friction related changes. Just for an example you can change a bushing size and maybe you see seating change 10 pounds. But you can do something that effects friction like clean the neck to bare metal or lube it and see 50+ pounds. So seating force is "mostly" a measure of friction.

Some folks just can't get a grasp on this no matter what.