neck turning help


Well-Known Member
Feb 1, 2009
hey guys, I want to start turning my necks for my .30-06.

I have a ball mic and a forster outside hand neck turner coming in the mail.

question is how much do I cut without getting to thin? I'm using winchester brass and using calipers (i know not that accurate) I get measurements from .0115 to .015 in thickness variation. I was thinking of turning to uniform the brass to .012. Would that be too thin??? Using a Lee collet die to size the necks..

Thanks in advance guys.
Sounds like you're committed. You must have already considered what you want..

You want uniform necks with not alot more than 2thou of sizing needed. So what do your fired necks measure fresh out of the chamber? You'll want your loaded necks to measure ~1thou less after turning.
So if your chamber neck is .334" you'll be good with LOADED necks measuring .308 +24(.012x2)=.332", leaving FIRED brass measuring .333(after springback), and 2thou sizing to get .331, providing ~1thou tension(after springback using a .3300 -.3305 bushing).
Or take your [(chamber neck - .308 - .002) /2] for a thickness starting point.
Wait for your ball mic. Your brass may not be as bad as your calipers are measuring. If in fact you do have necks from .0115" to .015" then you have a problem. But if you want to use it anyway then you should turn it to .013" or so. The rule is not to turn thinner than .010" but that is minimum thin. I have 3 rifles with tight necks and turn to .012", .013" and .013".

If you don't have a tight neck then just pick a happy medium that gets the most of your brass as close to the same dimensions as possible. With the Lee Collet then you will push the variances to the outside and it won't effect your bullet runout as much. But the thick/thin variance will make a difference in bullet release so pick a medium.

If you only have a few that are thinner than .013" and the majority are .013" to .015" then turn to the lowest denominator. You can also sort them if you have 50% or so that are consistant then use those for your prime brass and shooting.
thanks guys,

I"m getting some really good groups but getting some brass that are flyers. Last group I shot at 200 yards measured .583" outside to outside 3 shots, the next two were flyers. Took the same 5 brass reloaded them and marked them and the 3 good shot brass did the same at 200yards and the other 2 still flyers almost in the same spots....I've started pulling the brass that have flyers have noticed my groups improving, but unfortunately it's a lot of brass...I'm hoping that neck turning will help to uniform my brass a little bit more....
I assume this 30-06 has a factory barrel, not a custom barrel with tight neck dimensions. In a factory cartridge, there is normally .005 - .006 clearance on a loaded round. You do not need to turn necks. If you want to uniform the necks, you can lightly turn them by skimming just slightly (you will be able to see barber pole turns on the necks).

Since you are getting flyers, I suggest you check the concentricity of the loaded rounds. This can cause flyers, especially if you are using a sizer die with an expander ball inside.
I guess I need help as well

Sorry will open seperate thread
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Actually, it's a custom build with a mcgowen heavy barrel with a tight chamber. I don't know the exact neck diameter though. I just want to uniform my necks so they have consistent neck tension from round to round. I've noticed a handfull of brass in my loads that I can visually see different thickness around the case mouth.

you are correct, I'm trying to reduce my runout. Don't have the concentricity guage yet. Trying to get the tools to make straight brass first.

I don't use an expander ball. I size using a redding body die and the lee collet die for the neck.

Going to trim with a wilson trimmer, deburr with sinclair tool.

I was contemplating weighing brass, but it seems as though it's really the volume that I'm concerned about.

Just trying to minimize the variables. I know what the potential is .25moa or better, just want to get rid of the wacky fliers that seem to follow the brass. (i.e. flyers out of one brass remain flyers reloaded subsequently)

how far down do I turn? Just above the line of where the shoulder meets the neck? or do I cut into that line?
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Brass thickness grows consistently from the mouths downward to the webs.
It is thicker in the necks nearest the shoulder junction than at the mouths, and thicker still in the shoulders.
When you fire the brass the first time(fireforming), the brass expands pretty much everywhere. When the necks expand some of the shoulder junction becomes neck. Picture putting both your hands into a neck and pressing outward to see it expand into the shoulder.
Now, if you've turned to the shoulder junction and stopped, your neck thickness measures correctly on this fired brass until right at the NEW neck shoulder junction. Here you'll see full-unturned thickness(donut).
There are various ways to deal with it/prevent it, and turning is one of em.
You prevent it by turning past the neck, right onto the shoulder portion that will end up neck. You're not gonna wanna go crazy here as too much can cause seperation on firing. It is also very unlikely that your cutter shoulder relief angle matches your case shoulder angle. But this part of the neck serves no purpose other than to stay together, and stay out of your bullet seating way.
So just turn up onto the shoulder a bit(~.020") past the neck, removing about the same amout of brass as you have with the neck.
Now, the new neck area will be as thin/or less. No donut(for now)..

It can form again down the road depending on case body taper, shoulder angle, chamber, sizing and loads. If your cartridge needs constant trimming, you'll be there soon. Some turn to neck reaming to remove it later, but I wouldn't. I'd toss it and consider a better cartridge design -next time.
Some, forming wildcats, are producing necks too long for turning to address donuts. Some turn after fireforming, which makes no sense at all to me. Some cartridges lose neck on fireforming, and so donuts aren't an issue for them.
After turning, before fireforming, I pre-expand necks with a Sinclair turning mandrel one cal up. It this point I measure thickness to the junction with a ball mic. Then I neck size back down leaving a false shoulder for initial headspacing. This locks in my desired results, right from the git-go.

TomH is helping you alot by pointing toward Sinclair's turning system. You cannot go wrong to start right there, as you'll be ending right there too.
IMO, it's the best system. Well, actually, it's the only 'system' I am aware of..
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Do-nuts are where the shoulder brass flows toward the neck and causes a ridge at the shoulder/neck junction. The easiest way to tell if you have one is to insert a bullet into the neck of a FIRED & UNSIZED case. If the bullet will not go past the shoulder/neck junction then you have a do-nut

Another way is to get a set of pin gauges



The only way to get rid of them is to inside neck ream. Since you are getting the Forster, they do make a reamer that will fit the outside neck turner. The reamers are .003" over caliber diameter so if you set your brass up for .003" neck clearance in your chamber, then when you once fire you will have .003" inside neck clearance and can insert a reamer into your outside neck turner.

The way to tell the size of your neck in your custom chamber is to measure the OD of a FIRED/UNSIZED neck. You may have to allow for springback but it will be close.
thanks for the tip...what's this "donut" I keep reading about? how do I prevent it?

Since you have a Wilson trimmer they also make inside neck reamer get them from Sinclair.
- Wilson Neck Reamer

You may not see it but good to have inside reamer just in case. I see it more when forming cases. I don't turn pass the neck/shoulder junction normally once the case blows out some of the neck may be around that junction. Don't get me wrong I control the donut by inside neck reaming plus I use a Hart turner alittle better.
Robert W. Hart and Son Inc. Online Store
As you see neck turning can be a drain on the pocket book one thing leads to another.
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Someone on another forum said that the doughnut usually forms when resizing but won't form if using a lee collet die? I didn't think the collet die sized down that far down into the neck/shoulder junction.

I guess I better get a neck reamer too huh? how do I remove just the doughnut with the neck reamer and not the rest of the inside of the neck making it too thin??
Turn necks to the neck-shoulder junction.

Donughts: Remember, if you do not seat bullets at the base below the donught, they can be ignored. Only when the base of the bullet touches the inside doughnut, are they a problem.
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