Turning to those with more experience. I'm necking down new brass to a smaller caliber using a Redding type S Full Length sizing die. The new brass has some neck thickness variation, should I turn the necks before resizing or wait until they are necked down to turn, in order to avoid runout?
Neck turning runout question
- Thread starter mtang45
- Start date
My concern with turning after necking down is that neck thickness variation is likely pushed to the inside with the bushing, making the inside of the neck not concentric. If I turn at that state then I'm making the neck walls consistent but the neck will likely be off center. I could be all wet in my reasoning, and that's why I turned here.
Well looks like you are sizing with a bushing die. That doesn't work well for.necking down or sizing for turning.
Now you could neck down with your bushing die, check and make sure a piece of unloaded brass chambers OK, then load and fireform.
But even then to properly size the brass for turning you need to use a standard full length sizing die without the expander. Then expand the neck with the proper expander mandrel for turning
Now you could neck down with your bushing die, check and make sure a piece of unloaded brass chambers OK, then load and fireform.
But even then to properly size the brass for turning you need to use a standard full length sizing die without the expander. Then expand the neck with the proper expander mandrel for turning
Size your Brass down, then run over the appropriate sized mandrel to push inconsistencies to the outside. Very easy and brass should come out within .0005,
You turn on a mandrel, so unless the mandrel isn't round, that is of no concern.
Tech Line & Tips (FAQs)
Concentricity Problems - Redding Reloading Equipment: reloading equipment for rifles, handguns, pistols, revolvers and SAECO bullet casting equipment (redding-reloading.com)Concentricity Problems
We have conducted many tests over the years on the various factors contributing to concentricity problems with bottleneck cases. We have repeatedly found a definite correlation between the uniformity of the brass (or lack of it) and the resulting concentricity of the neck to the body of the case.
An interesting experiment also revealed that neck turning of brass that was intentionally sorted as non-uniform, showed little or no concentricity improvement when used in standard S.A.A.M.I. spec chambers. Conversely brass that was sorted and selected for uniformity remained uniform and concentric with or without a neck turning operation.
What Redding is saying above is you can turn your case necks, "BUT" turning the necks doesn't mean the neck will be aligned with the case body.
The same FAQ also tells you if the neck thickness varies .002 or more then size the neck severial thousandths smaller and use the dies expander to set the inside diameter.
I use the Redding neck thickness gauge below to sort brass "BEFORE" skim turning brass in a SAAMI chamber. Bushing dies work best in tight neck chambers with "good" neck turned brass. Also note the more the neck diameter is reduced in diameter the greater the chance neck runout will be induced.
Bottom line, there is a reason why so many reloaders use a Lee collet die. And this is because the Lee collet die produces less neck runout. And I would never use a bushing die to reduce the neck diameter when forming cases to a smaller or larger caliber. And this is because the bushing floats and can even tilt when sizing the neck.
"And I would never use a bushing die to reduce the neck diameter when forming cases to a smaller or larger caliber. And this is because the bushing floats and can even tilt when sizing the neck."
So how would you neck down, say, a 224 to a 204?
It's a choice if the bushing floats, it doesn't have to.
So how would you neck down, say, a 224 to a 204?
It's a choice if the bushing floats, it doesn't have to.
Use a standard non-bushing full length die it will hold the case body and neck in alignment. Again a bushing can move from side to side and even tilt. And if you lock the bushing down how do you know the bushing is centered with the case body.
If you are forming cases with a bushing die they will never be as concentric as with a standard non-bushing full length die. And you can't make a silk purse from a sow's ear, I have had Remington .223 cases with .009 neck thickness variations. And these variations extended down the case body, and this is why I sore the cases with a Redding neck thickness gauge. With one twist of your wrist, you will know the quality and uniformity of your cases. "BEFORE" you think about neck turning and wasting your time.
And if you neck turn in a SAAMI chamber the neck will expand that much more. So you end up working the neck more reducing its diameter so what have you gained.
Sort your cases for uniformity and only skim turn the necks for a SAMMI chamber. And again the Redding bushing die FAQ tells you they saw no improvement in neck turning unsorted cases. So again if you neck turn a pig you will still have a pig when your done.
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^^ Respectfully disagree, but each to his own.
What guarantee does one have that the neck and body of a non bushing full length die are concentric?
I make ammo that runs less than .001" TIR on the bullet ogive and neck OD using a Redding body bump die and Redding neck bushing die and micrometer seater, with un-turned Lapua brass.
No, turn culled cases (with excessive thickness variance) while new and at factory formed cal.
Neck down & remeasure to see how close you are to desired. Trial & error a few till you nail the setting.
Turn the keepers at this setting.
Tell me what you have for cal & loaded neck OD now, and what you want with downsized & turned.
I can calculate the extra turn amount needed before downsizing. Get ya real close
Neck down & remeasure to see how close you are to desired. Trial & error a few till you nail the setting.
Turn the keepers at this setting.
Tell me what you have for cal & loaded neck OD now, and what you want with downsized & turned.
I can calculate the extra turn amount needed before downsizing. Get ya real close
I have new Remington 300 SAUM brass that I want to take down to 6.5 SAUM. I am planning on doing that in 2 steps. The first through a .313 bushing and the final thru a .290 bushing. Starting neck thickness is .015"
+1 on what mikecr has stated. After determining the amount needing to be turned before necking down, use a mandrel sized for the neck turner and turn the necks into the neck/shoulder junction prior to sizing down. This method should eliminate the problem of getting a donut @ the neck shoulder junction.
Chuck
Chuck
Thanks Mike
He shouldn't turn into neck-shoulder junction for downsizing.
That donut mitigating action applies with case upsizing.
When you upsize/fireform some of thicker shoulder real estate converts to neck.
This is immediate dount building, so it's a good move to thin this new neck area beforehand.
When downsizing some of the thinner neck real estate converts to shoulder. It's just opposite of donut building and actually leaves the neck-shoulder junction a bit thinner. You should not turn that area thinner still -when you plan to downsize.
That donut mitigating action applies with case upsizing.
When you upsize/fireform some of thicker shoulder real estate converts to neck.
This is immediate dount building, so it's a good move to thin this new neck area beforehand.
When downsizing some of the thinner neck real estate converts to shoulder. It's just opposite of donut building and actually leaves the neck-shoulder junction a bit thinner. You should not turn that area thinner still -when you plan to downsize.
Mikecr: When forming my 20 P from 223 brass with a Redding bushing FL die I wound up with a donut that caused some initial grief in load testing. I wound up getting a K&M neck turner with an inside cutter mandrel to remove the donut and did cut into the shoulder. I recently neck turned 400 rounds of 220 Russian Lapua brass and cut into the shoulder prepping for a 20 PPC. I hope I will not have any issues with a thin neck of the sized down cases near the neck/shoulder junction.
Chuck
Chuck
Shooter13
Gold $$ Contributor
This, right here! Correct!
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