I know this subject gets hit a lot and me being very new to reloading ,is it in prep work , equipment or the camber from which we cycle our brass through ?
What are the causes of runout ?
- Thread starter luckeeshot
- Start date
Measuring run out became a fad many years ago and I like many others started measuring it and looking for ways to reduce it. There were many different opinions but you have to measure with your equipment to know. For me the biggest contributor was the expander ball being pulled thru the neck on the resizing operation. I got rid of the expander ball and started using the expander mandrel and that helped a lot. Later the neck sizing bushings were offered which gave the option of reducing the amount of neck sizing. The bushings and the expander mandrel used together seemed to help some.
The most important question is what is it worth on the target? If you are a bench rest shooter or F Class shooter it may be important but you will have to do significant testing to see. A lot of folks have the opinion that it is important but not many have tested sufficiently to know.
The most important question is what is it worth on the target? If you are a bench rest shooter or F Class shooter it may be important but you will have to do significant testing to see. A lot of folks have the opinion that it is important but not many have tested sufficiently to know.
I have / shoot brass that has had donuts, been fired many times ( 6 BR. ) but just when I think that this load with lots of run out will surely be way way out of the others, it aint .
jepp2
Gold $$ Contributor
And this is made worse if your sizing die is under-sizing the case neck OD (almost all do). If the expander has to open the case neck more than 0.001", it will pull the neck off center in my experience.
But with all the reduction in runout, I have yet to see it translate to the target, FWIW.
The root cause of runout is thickness variance in the brass.
We let this witch out with sizing. More sizing, more runout.
Runout affects shooting results when it exceeds your chamber clearances. At this point you end up with chambered pressure points, that are never consistent.
Big clearances leads to greater sizing.
But rather than going to the root cause, people often reach for relief in ever bigger clearances, and more sizing..
Similar notions were applied to engine building long ago, and we were lucky to get 100kmi out of them.
We let this witch out with sizing. More sizing, more runout.
Runout affects shooting results when it exceeds your chamber clearances. At this point you end up with chambered pressure points, that are never consistent.
Big clearances leads to greater sizing.
But rather than going to the root cause, people often reach for relief in ever bigger clearances, and more sizing..
Similar notions were applied to engine building long ago, and we were lucky to get 100kmi out of them.
Good brass is most important followed by good dies. Brass runout with lapua 6br brass with good dies can regularly be under a thousands and with a wilson inline seater or top quality competition seater you can get 1-2thousands or less on loaded ammo. Range pickup plinking 223 brass with cheap dies will lead to much worse. I measured some at 15 thousands runout. Will your rifle notice the difference between 1 thousands and 2? Probably not. Will it notice 1 thousands vs 20 thousands? Yeah I think so.
All preceding make great points.
Expander balls on the down stroke are likely the most common culprits .
To make mine at a minimum, Annealing/ turned necks on mid grade brass/ F/L sizing (no-bushing), and K&M tension mandrels... Makes a straight arrow
Expander balls on the down stroke are likely the most common culprits .
To make mine at a minimum, Annealing/ turned necks on mid grade brass/ F/L sizing (no-bushing), and K&M tension mandrels... Makes a straight arrow
Fit
The biggest cause of neck runout with standard dies is if the expander is locked down off center.
All my rifles are off the shelf factory rifles and I get the least neck runout with Forster full length dies.
The Forster die holds and centers the case neck when the high mounted floating expander enters the case neck. Meaning the expander can not pull the necks of center inducing neck runout.
You can also have Forster hone the dies neck to your desired diameter if needed.
Below my Redding non-bushing full length die equipped with a Forster expander and spindle assembly. This modification greatly reduced neck runout vs dragging the lower mounted and "longer" Redding expander through the case neck.
You can also use any standard full length die, remove the expander and use a expander die and get the similar results.
With my standard SAAMI chambers I get more neck runout with bushing dies. And I believe this is due to the amount the bushing has to reduce the neck diameter. Bushing dies work best with custom tight neck chambers and neck turned brass.
All my rifles are off the shelf factory rifles and I get the least neck runout with Forster full length dies.
The Forster die holds and centers the case neck when the high mounted floating expander enters the case neck. Meaning the expander can not pull the necks of center inducing neck runout.
You can also have Forster hone the dies neck to your desired diameter if needed.
Below my Redding non-bushing full length die equipped with a Forster expander and spindle assembly. This modification greatly reduced neck runout vs dragging the lower mounted and "longer" Redding expander through the case neck.
You can also use any standard full length die, remove the expander and use a expander die and get the similar results.
With my standard SAAMI chambers I get more neck runout with bushing dies. And I believe this is due to the amount the bushing has to reduce the neck diameter. Bushing dies work best with custom tight neck chambers and neck turned brass.
urbanrifleman
Site $$ Sponsor
Keerect. Crooked brass is crooked and you cannot fix it. Straight brass is straight. I don't care how you hold your mouth when you size...
Fired brass coming out of a correctly reamed chamber should do it,lol
urbanrifleman
Site $$ Sponsor
Nope. Not really. If the brass has internal stresses going all the way back to formation at the factory and one side is stiffer and one side is softer, or thicker and thinner, no amount of straightening will fix it.
Junk brass is junk brass. No way to fix it. Except melt it down and make it over.
Ccrider
Gold $$ Contributor
Interesting theory. I know that the prices of brass that give me little t no runout, do so consistently after each firing.
Murray Brook
Silver $$ Contributor
Most certainly agree with all you said. I found that the best and cheapest way to reduce or practically eliminate run out was to use a Redding body die to size the case and bump the shoulder and a Lee collet die to size the neck. BUT as others have said it takes a very accurate rifle to make a difference on paper going from .004 to .001 run out.
I did a lot of testing on this subject in 1993 and one test that I ran was what happens to run out on multiple firings and sizings. On the first reload I got an average run out of 0.00170 with a standard deviation of 0.00081 for 100 pieces of brass. On the second reloading I got an average run out of 0.00227 with a standard deviation of 0.00107 for 98 pieces of brass. On the third reloading I got and average run out of 0.00182 with a standard deviation of 0.00073 for 92 pieces of brass. This was with Lake City Match brass in the M14. From this data I concluded that the run out did not increase with reloading.
More important, further testing did not show any correlation with run out and score on the target at 600 yards with the M14.
Dusty Stevens
Shiner
I gotta know what you were using to measure down to the hundred thousandth. Ive seen hundred thousand dollar cmm machines that couldnt do it.
With an analog dial indicator that measures directly to 0.001 you can estimate the next decimal place. Then when I average a significant number of data points I take the next decimal place as significant although it is probably worthless. That is the way I recorded the data in 1993 so I did not make the effort to round off in my reply. So if it matters to you or if it is a distraction simply take the third decimal place as read directly and the fourth decimal place as significant and drop the fifth decimal place. Either way, the message from the data analysis is the same.
Truths pass all tests, so if you've seen runout flatten, without qualification, then my broad statement is wrong.
But I'm pretty confident that at ~30 reload cycles, or 50, your runout numbers would be far enough apart to broadly reach a different conclusion.
Aside from my seeing it, there is logic behind it. Every time you force brass to yield (size it), you change it in a way that can never be exactly undone. Sure you can size it 3thou this way & then 3thou that way, but it's not the same as it was beforehand, and even annealing can't resolve that. It will soon take different efforts to go exactly 3thou this way & then 3thou the other way. We're braking granular structure with sizing, regrowing structure with annealing, but the original grains are now disconnected. Springback changes in amounts and directions. So brass personality changes.
This is small stuff but real. The witch fights you in making every case as you had before. Eventually, you end up sidelining some cases that just won't play with the others. And far enough down the road, every case in a batch will have taken their own personalities. Depending on the cartridge design, your chamber, your sizing, etc., this could be anywhere from 1 to 100 reload cycles.
If your goal is 1thou TIR, with a 30-06, forget that goal. If you ever reach it, you won't hold it.
For something like a 223AI, or 6Dasher, you could hold this goal for 50 cycles with minimal sizing. With a fitted chamber here, no sizing, you could go past 100 cycles with no concerns of runout. This is a good thing too, as runout in such a fitted chamber will not work well for results.
The relationship of runout and chamber clearances are connected -through sizing -of thickness variance, for both production of runout, and shooting results. A multiloop.
It's easy to make very low TIR ammo with a tight chamber, and you better do this to prevent chambered interference fitting (pressure points).
It's nearly impossible to make low TIR ammo with a sloppy chamber, but if sloppy enough to clear chambered interference from runout, then it doesn't matter.
Competitors have demonstrated excellent performance from either path.
If I were a competitor, I would chose the low clearance/low sizing/low TIR path. This, because it's easier to keep brass at consistent personality. That is, consistently resisting the pressure peak, through expansion, at consistent brass energy levels. My barrel(s) would always perform with the same batch of brass, heading toward or past 100 reloads, with minimal or no sizing.
That's just me though, and I'm not a competitor.
But I'm pretty confident that at ~30 reload cycles, or 50, your runout numbers would be far enough apart to broadly reach a different conclusion.
Aside from my seeing it, there is logic behind it. Every time you force brass to yield (size it), you change it in a way that can never be exactly undone. Sure you can size it 3thou this way & then 3thou that way, but it's not the same as it was beforehand, and even annealing can't resolve that. It will soon take different efforts to go exactly 3thou this way & then 3thou the other way. We're braking granular structure with sizing, regrowing structure with annealing, but the original grains are now disconnected. Springback changes in amounts and directions. So brass personality changes.
This is small stuff but real. The witch fights you in making every case as you had before. Eventually, you end up sidelining some cases that just won't play with the others. And far enough down the road, every case in a batch will have taken their own personalities. Depending on the cartridge design, your chamber, your sizing, etc., this could be anywhere from 1 to 100 reload cycles.
If your goal is 1thou TIR, with a 30-06, forget that goal. If you ever reach it, you won't hold it.
For something like a 223AI, or 6Dasher, you could hold this goal for 50 cycles with minimal sizing. With a fitted chamber here, no sizing, you could go past 100 cycles with no concerns of runout. This is a good thing too, as runout in such a fitted chamber will not work well for results.
The relationship of runout and chamber clearances are connected -through sizing -of thickness variance, for both production of runout, and shooting results. A multiloop.
It's easy to make very low TIR ammo with a tight chamber, and you better do this to prevent chambered interference fitting (pressure points).
It's nearly impossible to make low TIR ammo with a sloppy chamber, but if sloppy enough to clear chambered interference from runout, then it doesn't matter.
Competitors have demonstrated excellent performance from either path.
If I were a competitor, I would chose the low clearance/low sizing/low TIR path. This, because it's easier to keep brass at consistent personality. That is, consistently resisting the pressure peak, through expansion, at consistent brass energy levels. My barrel(s) would always perform with the same batch of brass, heading toward or past 100 reloads, with minimal or no sizing.
That's just me though, and I'm not a competitor.
When you full length resize a case with the expander removed it will be as concentric as it ever will be.
The runout problems can start with necks with neck thickness variations and compounded by the expander if lock down off center.
Many reloaders remove their dies expanders and use a expander die to expand the case necks to reduce neck runout.
And a Forster full length benchrest die with the high mounted floating expander works as well as using a separate expander die.
When reading replies in reloading forums you need to know who the neck sizer are and who the full length resizers are.
And expanders are not the end of the world as many people claim, you have no control over how much your necks expand in the chamber. But you can control how much the neck diameter is reduced by the die and enlarged by the expander.
And the military considers match grade ammunition to have .003 or less bullet runout. And a full length resized case has wiggle room to let the bullet be self centering in the throat. And the Late Jim Hull of Sierra bullets said the cartridge should fit the chamber like a rat turd in a violin case. A full length cartridge is supported in the rear by the bolt face and by the bullet in the throat. And the only part of the case that touches the chamber is the cases shoulder. (wiggle room and a rat turd in a violin case)
The runout problems can start with necks with neck thickness variations and compounded by the expander if lock down off center.
Many reloaders remove their dies expanders and use a expander die to expand the case necks to reduce neck runout.
And a Forster full length benchrest die with the high mounted floating expander works as well as using a separate expander die.
When reading replies in reloading forums you need to know who the neck sizer are and who the full length resizers are.
And expanders are not the end of the world as many people claim, you have no control over how much your necks expand in the chamber. But you can control how much the neck diameter is reduced by the die and enlarged by the expander.
And the military considers match grade ammunition to have .003 or less bullet runout. And a full length resized case has wiggle room to let the bullet be self centering in the throat. And the Late Jim Hull of Sierra bullets said the cartridge should fit the chamber like a rat turd in a violin case. A full length cartridge is supported in the rear by the bolt face and by the bullet in the throat. And the only part of the case that touches the chamber is the cases shoulder. (wiggle room and a rat turd in a violin case)
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