Standard FL Die vs. Bushing FL Die
- Thread starter brshtr
- Start date
Different shooters may have different goals but no one has a goal of increasing run out. So bushing neck sizing must also be about preventing or avoiding unnecessary run out.
Sure you can tune the length of the sizing and the amount of the sizing but you may cause run out if you only look at those parameters. I don't think many bushing shooters actually use them to adjust the length of the neck sizing. I know that I don't. I have a lot of bushing dies bought both new and used and not a single one has ever had any length of sizing adjustment. You might but the majority don't. There is not much length to adjust on many short neck rounds. If you are shooting short light bullets there is not much bullet shank length to adjust for.
Many shooters only use the hand type bushing dies for convenience, others for increasing case life, others because it is easy to make the die for a wildcat or odd caliber round.
When you are able to control all dimensions of the chamber neck and the case neck bushings can work really well.
If you have a chamber with a large neck the fired case may not neck size straight due to inadequate lead in or chamfer on the bushing. A FL die almost always has a nice lead in formed by the shoulder profile in the die.
Sure you can tune the length of the sizing and the amount of the sizing but you may cause run out if you only look at those parameters. I don't think many bushing shooters actually use them to adjust the length of the neck sizing. I know that I don't. I have a lot of bushing dies bought both new and used and not a single one has ever had any length of sizing adjustment. You might but the majority don't. There is not much length to adjust on many short neck rounds. If you are shooting short light bullets there is not much bullet shank length to adjust for.
Many shooters only use the hand type bushing dies for convenience, others for increasing case life, others because it is easy to make the die for a wildcat or odd caliber round.
When you are able to control all dimensions of the chamber neck and the case neck bushings can work really well.
If you have a chamber with a large neck the fired case may not neck size straight due to inadequate lead in or chamfer on the bushing. A FL die almost always has a nice lead in formed by the shoulder profile in the die.
Any centering you get is dependent on the neck being concentric to the case body. You cannot assume the bushing will produce concentric sizing. Some bushing have very small lead in chamfers and can force the neck to be sized off center.
Of course a full length sizing die sizes the neck. What I was referring to was using a neck sizing die only. Years ago I was one that believed the myth that neck sizing produced more accurate reloads and longer case length. I learned that neither of these assertions are true.
After being befriended by a few bench rest shooters I learned the error of my thinking. This was precipitated by developing functionality problems in the field with neck sized reloads, failure to feed and exact. They taught me how to properly full size using a .001 to .002' shoulder bump and I've never looked back. I'm sure bushing dies produce more uniform reloads but I've never used them.
The point I was trying to make is that I've achieved excellent result with standard full length sizing dies. BUT - excellent for me may not be excellent for target shooters. I'm not a bench rest shooter - God Bless those guys but I'd go insane shooting off a bench round after round. My entire focus in on performance in the field since I'm a varmint and predator hunter although I spend a fair amount of time on the range practicing off the shooting sticks. My accuracy standards are high but not as high as a target or bench rest shooter. I guess these esoteric discussion are of value to bench rest shooters but drive me nuts - no offense intended.
The root cause of runout is sized thickness variance. This thickness variance is inherent to brass manufacture, and runs from webs to mouths. The greater you size it in both or either amplitude or area, the faster runout grows. With FL sizing the entire case, runout is not created in just the neck, but the entire sized portion of any case with thickness variance. So whether you turn necks or not, FL sizing reduces you odds of straight(low runout) ammo. Separating and using cases with lowest thickness variance helps with every bit of runout, and so does minimal clearances and minimal sizing.
Looking at sizing of necks in itself, this is the same as sizing bodies with thickness variance. The greater the sizing, the greater your odds of creating runout. Turning necks helps with that much of your runout.
Where you choose or have to FL size, you roll body brass upwards, trimming it away. Some moves into neck/shoulder junction(donut area). There is just nothing good in sizing of this donut area, which brings it into play with tension, and can add to runout (never subtracting from). And there is no actual need to FL size necks, so it makes no sense to do so.
Some around I'm sure, at least try to manage and match their neck tensions. I'm sure that some around here have figured out that LR precision is pretty difficult with much in tension variances. They likely figure out that tension variance is tied to tension amplitude. That is, the lower your tension, the lower your variance of it(in grip force). Bushing dies enable us to adjust tension separate from our body sizing adjustments. This is, or should be, the reason for popularity in bushing-body dies ('FL bushing dies'). Some, like me, completely separate control with body die sizing, followed by bushing neck die sizing, followed by mandrel pre-expansion. I have produced ammo with this so straight that it's runout is below practical measure. And I know there is not a 'problem' with bushing neck sizing and runout.
Now, I may be the only reloader on Earth that adjusts and matches tension. Hard to believe though..
I do adjust my tension via neck sizing length, which I can control with shims/caseholders. I indirectly measure this with carefully controlled friction and a load cell instrumented expander mandrel die.
There is something important you need to know about partial neck tension adjustments. You aren't adjusting tension with interference fit. Provided your length of neck sizing is no more than seated bearing(normal), and provided your interference fit represents at least full spring back amount (~1thou)(normal), the only way to adjust tension is with bearing area gripped by that spring back. This is length sized against given seating.
You can size down more here(say -5thou), but the seating bullet will merely expand the neck right back out. Then if you were to pull the bullet and remeasure necks, you would see they spring back only ~1thou. That is all that grips bullets. That force per the length(area) of bullet bearing it's gripping.
How do you adjust this with FL sizing of necks? YOU DON'T.
And if you don't understand and consider all this, YOU SHOULD.
Looking at sizing of necks in itself, this is the same as sizing bodies with thickness variance. The greater the sizing, the greater your odds of creating runout. Turning necks helps with that much of your runout.
Where you choose or have to FL size, you roll body brass upwards, trimming it away. Some moves into neck/shoulder junction(donut area). There is just nothing good in sizing of this donut area, which brings it into play with tension, and can add to runout (never subtracting from). And there is no actual need to FL size necks, so it makes no sense to do so.
Some around I'm sure, at least try to manage and match their neck tensions. I'm sure that some around here have figured out that LR precision is pretty difficult with much in tension variances. They likely figure out that tension variance is tied to tension amplitude. That is, the lower your tension, the lower your variance of it(in grip force). Bushing dies enable us to adjust tension separate from our body sizing adjustments. This is, or should be, the reason for popularity in bushing-body dies ('FL bushing dies'). Some, like me, completely separate control with body die sizing, followed by bushing neck die sizing, followed by mandrel pre-expansion. I have produced ammo with this so straight that it's runout is below practical measure. And I know there is not a 'problem' with bushing neck sizing and runout.
Now, I may be the only reloader on Earth that adjusts and matches tension. Hard to believe though..
I do adjust my tension via neck sizing length, which I can control with shims/caseholders. I indirectly measure this with carefully controlled friction and a load cell instrumented expander mandrel die.
There is something important you need to know about partial neck tension adjustments. You aren't adjusting tension with interference fit. Provided your length of neck sizing is no more than seated bearing(normal), and provided your interference fit represents at least full spring back amount (~1thou)(normal), the only way to adjust tension is with bearing area gripped by that spring back. This is length sized against given seating.
You can size down more here(say -5thou), but the seating bullet will merely expand the neck right back out. Then if you were to pull the bullet and remeasure necks, you would see they spring back only ~1thou. That is all that grips bullets. That force per the length(area) of bullet bearing it's gripping.
How do you adjust this with FL sizing of necks? YOU DON'T.
And if you don't understand and consider all this, YOU SHOULD.
Hi Dave,
I kept detailed records comparing run-out on multiple full length bushing to full length non-bushing dies: many samples. Sometimes the bushing dies produce great results, but the non-bushing produces straighter cases on average in my experience. It's more convenient to change the neck tension with bushing dies. You have to keep several different non-bushing dies to accomplish the same thing. Then if you decide to turn necks to a different thickness, you might need new non-bushing dies with new neck sizes. That said, I made custom F/L non-bushing dies for my competition cartridges and am very happy with the results. More expensive, more hassle, but better runout for sure. About half my cases have zero runout and the rest are less than .001...every time. In addition to custom dies, you could have Forster or Hornady hone the necks of their standard dies to your desired size(s).....less expensive option.
Not true. There is more than one cause of run out.
I can give you the same equipment that causes it and it will also cause it for you regardless of what you think causes it.
I can give you the same equipment that causes it and it will also cause it for you regardless of what you think causes it.
FL bushing. The unsized neck centers the round in chamber.
Does it?
How much over .276” is the chamber’s neck diameter compared with how much over a bullet’s diameter is the throat?
Where’s the case neck going to do its best to be with an ignited primer blown back against the bolt face so shoving the case’s shoulder squarely into the matching socket of the chamber’s shoulder?
I was referring to the ROOT CAUSE of runout, independent of problems with equipment or methods.
Yes, we cause runout many different ways, but even if we didn't, sizing of thickness variance is still there,, still causing runout.
So no matter what you do, you have to remove sizing of thickness variance to eliminate runout. Hence 'root cause'.
When you identify and remove any root cause, you better expose and ease elimination of mere contributors and side effects.
Centering the round in the chamber- 1. Bullet jammed into the rifling. 2. Tight head to datum of the brass, causing a slight crush fit when chambering a round. 3. Sizing 1/2 of the neck for factory chamber when the leade is so long or shot out, that bullet jam doesnt work.
My chambers neck is .276" My brass has been fired 15 and 18 times. The neck has fully expanded to the chamber neck in about 4 or 5 firings and no longer springs back. No annealing done.
As for the primer thing, the firing pin strike keeps the primer in place. In fact a Savage's 223 firing pin strike will set the shoulder back .006" We dont know this till you have a misfire with a defective primer. IMO.
Tension vie neck sizing length; and I wonder how many pounds are in one tension; or how many tensions are in 1 pound. I am impressed with the suggestion you may be the only reloader on Earth that adjusts and matches tension.
I say that because I am the only one that does not have a tension gage that measures tension; I do have tension gages, none of them are calibrated in tensions and I do not have a conversion for tensions to pounds.
F. Guffey
My being the only reloader looking at this was facetious.
I do not understand your meaning with tension units. From my perspective, it's a matter of force (any force unit) stored and recovering in a stretched hoop material (our brass necks).
For hoop tension measure that applies to bullet grip, we would need a pressure controlled expander. With this, we would ramp a force to cause 1thou of hoop expansion. This being fully recoverable for the hoop.
With necks matching in this attribute, we would know that same seated bullet bearing causing 1thou of neck expansion, is gripped with the same spring back force. Units of that condition could be in pounds per square inch.
Unfortunately, such a device has never been developed for us.
Otherwise, I'm confident we could also see that area and angle of body-shoulder to neck-shoulder, and neck void area beneath seated bearing also affects expansion forces needed for bullet release. Right now, we're just a long way away from knowing, understanding, and controlling this.
Mandrel expander insertion can indirectly show spring back force differences, provided friction in this action is consistent (removed as a variable). It will never be as accurate as direct measure would be. But it's what we have.
I know there are stretching machines to measure attributes of material yielding. But these are not hoop expanders, and our neck brass granular structure is changed with expansion (not length stretching). So I don't see these machines applying to our condition.
I do not understand your meaning with tension units. From my perspective, it's a matter of force (any force unit) stored and recovering in a stretched hoop material (our brass necks).
For hoop tension measure that applies to bullet grip, we would need a pressure controlled expander. With this, we would ramp a force to cause 1thou of hoop expansion. This being fully recoverable for the hoop.
With necks matching in this attribute, we would know that same seated bullet bearing causing 1thou of neck expansion, is gripped with the same spring back force. Units of that condition could be in pounds per square inch.
Unfortunately, such a device has never been developed for us.
Otherwise, I'm confident we could also see that area and angle of body-shoulder to neck-shoulder, and neck void area beneath seated bearing also affects expansion forces needed for bullet release. Right now, we're just a long way away from knowing, understanding, and controlling this.
Mandrel expander insertion can indirectly show spring back force differences, provided friction in this action is consistent (removed as a variable). It will never be as accurate as direct measure would be. But it's what we have.
I know there are stretching machines to measure attributes of material yielding. But these are not hoop expanders, and our neck brass granular structure is changed with expansion (not length stretching). So I don't see these machines applying to our condition.
jepp2
Gold $$ Contributor
Some good information that may be helpful to you in this recent Bulletin:
http://bulletin.accurateshooter.com...ading-checking-the-geometry-of-neck-bushings/
Thanks!
You are making this stuff? Or; repeating this stuff because you thought it sounded good? I have rifles with killer firing pins, I have posted results; you are posting rumors about what happens after the tiger is pulled. It started something like this; the firing pin strikes the primer and then the whole thing (the case, bullet, powder and primer) take off for the shoulder of the chamber and then the shoulder of the case hits the shoulder of the chamber and then the firing pins crushes the primer and then goes bang. And then I asked: "How much time passed between puling the trigger and the primer making that sound".
My killer firing pins crush the primer before the case, bullet and powder know their little buddy the primer has been crushed. And the person that made up that story left out part of the sequence of events and has never been able to figure out what part. And then there is that other part reloaders do not understand, if there was any truth to your story the shoulder would be against the shoulder of the chamber when fired and again I ask another question; "When the primer went bang where was the clearance?"
One more time; I fired a case with .127" clearance between the shoulder of the chamber and shoulder of the case
F. Guffey
Your doing the same as I do .FL bushing. The unsized neck centers the round in chamber.
My die moves the case and one and a half of the 1 1/2 under size of the chamber shoulder included .
The foward part of the neck is sized for bullet holding only.
With the bullet seated It never exceed the back half diameter . The boat tail is foward of the shoulder . So donut is never a problem.
No expand ball is ever used .
Thanks for the great pictures . Larry
I will try to type slower; I have tension gages, all of my tension gage measure in pounds. I have deflection gages, all of my deflection gages measure in thousandths and in pounds. I am the only reloaders that does not have a hang-up with 'bullet hold'. Somewhere in the past other reloaders took a shine to neck tension because it sounded cool; and now? They believe if they convince me I would be cool if I agreed with them I would be cool.
I can not think of anything sillier than a reloader claiming they have 5 tensions or 7 tensions etc. Some reloaders are moving to bullet grip but grip does not sound as cool as tension.
Back to the press that measures bullet seating pressure; the gage does not measure in tensions.
F. Guffey
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