Concentricity question

[savageshooter86]

I got a Sinclair concentricity tool and started checking some cases. Fired cases were 0005-001". Brass sized with Collet Die were 4-6 thous runout(using Coax press and Lee Collet die). Loaded cartridges were anywhere 4-6 thous. So went to friends house and sized a few cases using 335 bushing, then ran an expander mandrel through case after. Runout on these were 3 thous.(rockchucker press, Whidden Bushing die, expander mandrel)

Checked some virgin Lapua brass and go readings of 5-8 thous runout. His loaded rounds were 5 thous and a couple were just under 3

What am I missing here? Find it hard to believe both of us are experienced this much runout change from fired cases using 2 completely different sizing steps and presses

 

[Erik Cortina]

Are any of you turning necks?

Your runout is on loaded round or only on resized brass?

 

[savageshooter86]

I cleaned mine up about 95%. He didn't.

 

[jlow]

Are you checking runout in the same place for everything you mentioned?

Also how consistent are you readings? Specifically if you measure the same round/case three times, are you getting the same number? I had problems with that gauge....

 

[savageshooter86]

Yes reading halfway on neck and getting same reading each time I put the same case on the tool. I measured loaded round also on FGMM 168 ammo and runout on those were over 4 thous :-\

I am not 100% sure where on the bullet to place the indicator at but that is the last step of solving. The sized necks are out of whack too. So the seater isn't going to fix the runout by itself

 

[jlow]

Runout problem starts with the brass. The first thing I do when I get new brass is to check neck thickness consistency. If you got thickness variation around a case that is over 1.75 thousands, it gets tossed out of the box for precision reloading. Neck thickness variation means case body thickness variation to the same degree and that piece of brass is going to banana on you when it gets fired and there goes your concentricity. LaPua 308 is pretty good but Win 308 you will have to cull. Even with culling, uneven neck thickness is going to transfer directly to runout as the bullet is going to runout that amount - thus the reason to neck turn so that neck thckness variation is closer to a few ten thousands. Then the seating die cmes into play. The inline seater like the Wilson works best for me - after all that, final loaded round should be around 1 thousands.

Expander mandrel are generally bad for runout, and Lee collet die is the best. Bushing does not help if you don't have consistent neck thickness...

 

[savageshooter86]

well sounds like I should not be having an issue as I turned my necks and are all very consistent. 01425 thickness and turned all the cases. Checked several and after all being basically the same stopped checking. The collet sized brass should have been real close to 1 thous or less but they were not even close........

 

[22BRGUY]

Runout problem starts with the brass. The first thing I do when I get new brass is to check neck thickness consistency. If you got thickness variation around a case that is over 1.75 thousands, it gets tossed out of the box for precision reloading. Neck thickness variation means case body thickness variation to the same degree and that piece of brass is going to banana on you when it gets fired and there goes your concentricity. LaPua 308 is pretty good but Win 308 you will have to cull. Even with culling, uneven neck thickness is going to transfer directly to runout as the bullet is going to runout that amount - thus the reason to neck turn so that neck thckness variation is closer to a few ten thousands. Then the seating die cmes into play. The inline seater like the Wilson works best for me - after all that, final loaded round should be around 1 thousands.

Expander mandrel are generally bad for runout, and Lee collet die is the best. Bushing does not help if you don't have consistent neck thickness...

+1 for jlow....If you haven't already, you may want to invest in a ball micrometer....they're pretty cheap around at Graf & Sons or even Ebay. The case must then be fired in the rifle to get the benefit of the neck turning. If neck wall thickness is not consistant all the way around, sometimes its good to do an additional 40% cleanup after the first time and firing. + a BIG ONE on the collet dies with very light cam over. Best Wishes

 

[22BRGUY]

Can I ask which cartridge you are reloading....01425 seems pretty thick neck wall thickness to me is why I ask
Thanks

 

[savageshooter86]

308 win. Out of the box the brass was 15-16.5 thous. So I cleaned them up to try to have as consistent of neck wall thickness and therefor neck tension. We used a ball mic to set the turner up and we used it after to check the several cases

 

[jlow]

Not sure what your problem is, but virgin LaPua at 5-8 thousand seems high.. On the road now so can't check my data, so from memory -perhaps someone can comment from actual data.

 

[22BRGUY]

Have you had a chance to fire the cases after turning?

 

[savageshooter86]

Yes these are 2x fired on mine.

 

[gotcha]

Andrew, be sure the ball bearings at the case head are resting between the case web and the ejector cut (the roundest part of the case). If the bearing is above the web you'll usually find uneven roundness caused by variations in wall thickness above the web. These variances will be magnified at each firing until F/L sized. Just a hunch.

 

[22BRGUY]

I got a Sinclair concentricity tool and started checking some cases. Fired cases were 0005-001". Brass sized with Collet Die were 4-6 thous runout(using Coax press and Lee Collet die). Loaded cartridges were anywhere 4-6 thous. So went to friends house and sized a few cases using 335 bushing, then ran an expander mandrel through case after. Runout on these were 3 thous.(rockchucker press, Whidden Bushing die, expander mandrel)

Checked some virgin Lapua brass and go readings of 5-8 thous runout. His loaded rounds were 5 thous and a couple were just under 3

What am I missing here? Find it hard to believe both of us are experienced this much runout change from fired cases using 2 completely different sizing steps and presses

In looking at this closer it seems the runout is occurring as you size with the collet die. I wonder if there is a chance the collet in the die is bumping the shoulder a little bit in the process and adding runout. Maybe if you took a .010 or .020 shim or maybe even a thin washer with a 1/2" center hole and put it over the case and on top of the shell holder to "partially' size the neck with the collet die, which would make sure the collet would not possibly be touching cartridge shoulder, and then seat a bullet and check the runout of the bullet, it might show if that is what's happening. Would also suggest setting the collet die where it would just have a light camover feel to it. Just a thought if you want to try it.
Best Wishes again

 

[savageshooter86]

Those tricks could help, but I am using CoAx press.

Also experienced 3 thous runout using other press and bussing die and expander die. So 2 different presses and sizing methods giving decent increase in runout

 

[jlow]

I got a Sinclair concentricity tool and started checking some cases. Fired cases were 0005-001". Brass sized with Collet Die were 4-6 thous runout(using Coax press and Lee Collet die). Loaded cartridges were anywhere 4-6 thous. So went to friends house and sized a few cases using 335 bushing, then ran an expander mandrel through case after. Runout on these were 3 thous.(rockchucker press, Whidden Bushing die, expander mandrel)

Checked some virgin Lapua brass and go readings of 5-8 thous runout. His loaded rounds were 5 thous and a couple were just under 3

What am I missing here? Find it hard to believe both of us are experienced this much runout change from fired cases using 2 completely different sizing steps and presses

In looking at this closer it seems the runout is occurring as you size with the collet die. I wonder if there is a chance the collet in the die is bumping the shoulder a little bit in the process and adding runout. Maybe if you took a .010 or .020 shim or maybe even a thin washer with a 1/2" center hole and put it over the case and on top of the shell holder to "partially' size the neck with the collet die, which would make sure the collet would not possibly be touching cartridge shoulder, and then seat a bullet and check the runout of the bullet, it might show if that is what's happening. Would also suggest setting the collet die where it would just have a light camover feel to it. Just a thought if you want to try it.
Best Wishes again

This is an excellent point. Troubleshooting is best done by isolating the variables and not looking at the final product as frequently the are more than one problem.

In your case, one of your first step (LCD) already appears to be giving you trouble so I would not go pass that until you figure out what it is before moving on. Questions like how good is your starting brass? Was it good in term of thickness variation? How good was your neck turn? is the LCD working properly? etc.....

 

[savageshooter86]

I didn't have this tool right after neck turning to check. So I am only going by my 2x fired brass that has not been sized again yet.

Will look into this more.

I guess I could have them re neck turned down to 014 or less(as suggested by a couple people on here). This would clean them up and I could check runout and sort then. But then that would give me more clearance in the chamber, as the new rifle will be a Savage FTR 308 win.(assume this is going to have a 344 neck also)

 

[jlow]

The neck turn may be part of your problem but unless something really went wring there, it's not going to give you 4-6 thousands runout that you see after the LCD from 0.5-1 thousands....

Take at least 5 piece of brass that you have fired, check runout, neckturn it, check runout, size with LCD, check runout. Do each measurment 3 times and keep track of which one is which and this should pinpoint your problem.

 

[mikecr]

There are a few squirrely things posted about this.
For one, firing cases does not cause runout. F/L sizing does not reduce runout. It's just the opposite.
Cases are as straight as they're ever going to be right out of a smoking chamber. Anything you do to them from there brings out the runout.
This is why it's best to do as little as required in sizing(for runout).
It's also why it pays to cull brass by thickness variance, right up front.
Second, it's a bad idea, and not needed, to turn necks after firing. Turn them correctly while new.
Fired necks are never again gonna fit a turning mandrel well enough for better precision.

Also, there is nothing wrong with this Sinclair runout gage: http://www.sinclairintl.com/reloading-equipment/measuring-tools/concentricity-gauges/sinclair-concentricity-gauge-prod37479.aspx
They merchandise it as a concentricity gage, but it's really a runout gage, which is just what you need to verify straight ammo.
If by mandrel, you mean this: http://www.sinclairintl.com/reloading-equipment/case-preparation/neck-turning/turning-expander-mandrels/sinclair-expander-mandrel-oversized-prod33134.aspx there is nothing detrimental in it's use. Another just the opposite as this pushes thickness variance outward so bullets don't have to(bullets are terrible expanders), and so they seat straighter.

You should be measuring loaded runout off bullets. This removes neck thickness variance(pushed outward by bullet) from measure.
New brass will always have higher runout than recently fire formed brass, unless your chamber is out of whack. There is no reason to measure/fuss over runout, loaded or not, on new brass.