Neck turning


Well-Known Member
Aug 22, 2021
West Haven
What is the thinnest you would turn your necks to? I have Winchester brass for my 7mag and before turning it’s reading spots that are 9 thou to 12 thou.
What is the thinnest you would turn your necks to? I have Winchester brass for my 7mag and before turning it’s reading spots that are 9 thou to 12 thou.
We don't go any thinner than 12.5 and sometimes 12.0 with 0.223 or 0.204.
How are you measuring?
Should be using a "Ball Micrometer" to measure neck wall thickness. you don't want to use just a regular Micrometer with Blades to measure wall thickness.
I would sort those out. .009 is really thin. .012 after turning would be a bit more normal. If you're just cleaning the high spots to get the neck walls consistent, turn them all to .012 and check the non cleanup with a ball mic. Keep in mind that your die doesn't know what you're feeding it. Be nice to cull out the really thin ones (bad neck tension) and keep the ones that clean up within .001.
Turn necks & stop using an expander button in your F/L die, Amount of neck turning depends on chamber. Neck turning amount is ideal when nice slip fit is obtained with bullet & fired brass. uniform neck tension, reduce cold working & extend brass life. Chamber dimensions are set by SAAMI specs.

My 6.5 rounds after firing measure .297 (brass spring back) and upon bullet seating measure .290, (.003-.004 radius reduction). Neck wall thickness = .290 - .264 = .026 / 2 = .013, that neck wall thickness provides a nice slip fit, minimum work hardening, adequate neck tension & cleanup for minimal run out. Brass neck wall thickness may vary .001 or more but turning make neck walls uniform,

Periodic annealing helps to reduce brass spring back.

Ball micrometers are needed for measuring neck wall thicknesses, but ordinary calipers can suffice to determine diameters that provide nice slip fits of bullets into fired cases.

The next problem is setting up the neck turning devices for accurate repetitive neck turning among different cartridges, bullet diameters & chambers - next to impossible or real difficult. I need to get better stuff or by separate neck turners for each chamber.
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My 6.5 rounds after firing measure .297 (brass spring back) and upon bullet seating measure .290, (.003-.004 radius reduction).
Your chamber neck is ~.298 and your loaded necks are .290?
~8thou neck clearance? You downsize 7thou + desired interference with FL sizing?

Cnkhunting, you should carefully measure your brass, find the mean, and cull out offenders.
Determine your existing chamber clearance and decide if you need to turn anything -or if that would be the worst thing you could do.
Neck turning is not automatically the right thing to do.

To measure neck thickness correctly you need to pick & set a datum point. Half way down the neck should be fine.
If you allow the datum in measure to shift, then thickness readings will shift, as brass tapers in thickness from webs to mouths.
And as you measure radially around necks, note extremes in thickness variance. Thickness variance also runs webs to mouths.
This thickness variance and sizing of it causes runout. So if you size case bodies having a lot of thickness variance, your runout will grow regardless of neck turning. Best to cull it out same as culling out overall thickness departures from mean.
Doing this correctly will buy you way more than neck turning.
Yes, works just fine. After firing this "datum" point will vary in location. Don't toss good brass.

Neck turning would be required should a bullet (used as a gauge) not easily slip fit into case mouth. The general idea being avoiding pressure spikes and inconsistent neck tension by providing .002 - .003 radius for neck/chamber clearance upon firing with neck expansion.

From Redding (die manufacturer)

"Now anyone with a standard reloading press can benefit from advanced benchrest techniques.
The amount of resizing provided by conventional reloading dies has always been dictated by the manufacturing tolerances (SAAMI specifications) of the brass cartridge case itself. Reloading die manufacturers have been forced to design the neck diameter of their dies small enough to accommodate the thinnest possible brass.

This may be as much as .008" - .010" smaller than the maximum cartridge dimensions typically shown in most reloading manuals.

Since the majority of cases that the reloader is likely to encounter in the field are thicker than the minimum specifications that the dies were designed for, case necks are often resized excessively.

It can be easily demonstrated that excessive resizing of the cartridge case quickly leads to stress distortion and concentricity problems. The new Type S - Bushing Style Dies offer a simple solution to this age old problem."

This gives some idea of why bushing type dies are useful. It also provides justification for neck turning to prevent - "excessive resizing of the cartridge case" & " since the majority of the cases that the reloader is likely to encounter in the field are thicker than the minimum specifications that the dies were designed for, case necks are often resized excessively"

Turning necks a reasonable amount makes for consistent neck wall thickness, concentricity, and minimum work hardening. For 6.5 rounds, a .003 radius reduction works just fine and provides .013 neck wall thickness (no "interference" ?) and will clean up any variations of neck wall thicknesses.

Neck turning has improved 600 yard scores and brass life with .308 Win loads, like over some 1500 - 2000 round barrel life.

It should be noted that Forster provides a service to "hone" out or increase the diameter of the neck portion of their F/L dies. My 6.5 Forster F/L dies are enlarged for a die neck diameter of .288. This would provide the same amount of neck sizing as a .288 bushing die - providing adequate neck tension to hold bullets securely.

Cartridge brass is subjected to pressures often exceeding 60K psi and gradual neck thickening is expected but will vary from each piece of fired brass - like expect it to happen. Tossing good brass or "cull out" using some "mean" (average) taken at some arbitrary location to determine suitability for reload is unnecessary & wasteful. Some brass goes for over $1.50 per piece. Take control of the situation - turn necks to make neck walls uniform. F/L size turned neck brass with no expander button.
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This is now being considered because I plan to get a new 6.5 PRC barrel.

Some photos of dummy rounds being attached to project for chamber conformation.

IMG_1926 (1).JPG

IMG_1927 (1).JPG

IMG_1928 (1).JPG

These are some Hornady 6.5 PRC range brass (like free) that I have had for about 1 year. Observe the neck diameter is .290 +- .001 using caliper measurement. Observe the necks have not been completely turned down. The necks were sized with a unaltered Forster F/L die with expander, then expanded with a Lee .262 mandrel, then .264 bullets were seated. Neck wall thickness = .290 - .264 = .026 or .026/2 = .013 neck wall. Two other dummy rounds were assembled, all indicate partially turned down necks. Complete neck turning for uniform neck wall thickness with loaded round necks would make for diameters of .289. Turning necks down to .288 would still provide adequate neck tension & less work hardening & neck wall thicknesses of .012.

Do I think neck turning is needed? Yes - Necks show diameter/radius variations. Different brass lots may have thicker neck walls. Brass neck walls thicken with brass flow. Neck turning reduces neck wall thickness & reduces work hardening with unaltered factory F/L dies. Expander button not needed for F/L sizing with turned necks.
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I’m not a 7 rm expert, but I would expect with a ball mic you would see 0.014” nominally.

i would be hesitant to go thinner than 0.012”, but I have no reason for that.
Its possible to neck turn brass & still use standard fl dies. The reverse of a honed neck die.
Sure is- I do this all the time. Quit turning upon complete clean-up & easy slip fit of bullet into fired case.

In response to the magnifier man - .003 to .004 radius reduction is not excessive. Turned brass does not need an expander button.

Happy memories of neck turning 500 (less then 10 matches) or so .308 W cases used for match shooting by chucking a Forster neck turner in a drill press. This provided uniform neck wall thicknesses, minimum run out, extended brass life (no expander button), and uniform neck tension (bullets easily slip fit into fired cases). Brass was 7.62X51 GI Match Brass, LC, no primer crimp, scrounged free from Army team. 600-yard scores averaged 194 plus, with many X's - would have made Master class except for standing scores & job transfer to Alaska. The nice shiny necks looked cool. 168 Sierra MK's then 168 Hornady match bullets, H380. RWS primers.
To the OP, I often look for brass brands on the thick side so I can turn to my optimum size and I never turn brass below .013” anymore.
I also use chambers now where my happy clearance is at .003” minimum, and .0045” maximum. I don’t own a single ‘neck turn only’ chamber reamer anymore either.
If I can, I neck size DOWN to achieve my perfect brass fit. My 264WM‘s are a perfect example. I have a few hundred ww-super cases acquired in the very early 90’s that are .014-.0145” which I skim turn to .013”, as I have a few rifles as chambered, I also size down Remington 7RM brass to 264WM, and it turns out these will clean up at .013” as well. So I get my .003” clearance and I can turn about 80% of the neck as I only size this much anyway.
Thin necks, as is normally found on some brands like Norma, depending on chambering, often have issues with deformation which I try to avoid due to donuts and splitting.


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