neck thicknesses

[ARlife4me]

is there a "best" or "better" thickness for necks in regards to longevity, spring back and/or tension? forget about accuracy and pressure for the time. is there a good comparable average that's acceptable? spring back might not be limited to hardness if necks are to thick? if the chamber is reamed to accept the brass of thicker necks, would it still be workable? cartridge and caliber might not have anything to do is this, but if neck tension is well enough to hold the bullet would it still make any difference?

just wondering as for designing a cartridge is question reasons.

 

[MagnumManiac]

One thing I will tell you about necks, there is no magic thickness, only clearance in your chambers, this NEEDS to be .003" MINIMUM. If your neck does not allow this because it is too thick, then it needs turning down.
Personally, I like neck thickness to be uniform at .0135"-.014" and no thinner. Several brands of quality brass fall into this and that's what you base your chamber on, not the other way around.

Cheers.

 

[ARlife4me]

One thing I will tell you about necks, there is no magic thickness, only clearance in your chambers, this NEEDS to be .003" MINIMUM. If your neck does not allow this because it is too thick, then it needs turning down.
Personally, I like neck thickness to be uniform at .0135"-.014" and no thinner. Several brands of quality brass fall into this and that's what you base your chamber on, not the other way around.

Cheers.

at the thickness you prefer it at is more of a preference than what wouldn't work? clearance is understandable for proper chambering and extracting and would do a chamber to match brass numbers. say if i went with .020" on a 30cal (.308") then chamber neck needs to be .351 or .354 to be clear?

 

[MagnumManiac]

The thickness I prefer is based on numbers taken from the brass I chose, which just so happens to be accommodated by several brands, then I cut the chambers to suit. To make the brass fit, it needs turning to be .014" at the upper end or .0135" at the lower end.

What you're quoting, being .351"-.354" is probably close, but I would have a solid finished neck number FIRST to work off, no point cutting your chamber then discover it's too big or small. What brass has .020" thick necks?
The clearance is necessary only so the neck expands, if it doesn't and pinches the bullet, it will give you very high pressures.
When designing a chamber for custom applications, you need all dimensions first. SAAMI is very bad at making chambers too large, it's unavoidable because ALL brass has to fit it, but YOU can control this with a custom reamer.
Even a 'Match' chamber can be too large.

Cheers.

 

[ARlife4me]

The thickness I prefer is based on numbers taken from the brass I chose, which just so happens to be accommodated by several brands, then I cut the chambers to suit. To make the brass fit, it needs turning to be .014" at the upper end or .0135" at the lower end.

What you're quoting, being .351"-.354" is probably close, but I would have a solid finished neck number FIRST to work off, no point cutting your chamber then discover it's too big or small. What brass has .020" thick necks?
The clearance is necessary only so the neck expands, if it doesn't and pinches the bullet, it will give you very high pressures.
When designing a chamber for custom applications, you need all dimensions first. SAAMI is very bad at making chambers too large, it's unavoidable because ALL brass has to fit it, but YOU can control this with a custom reamer.
Even a 'Match' chambers can be too large.

Cheers.

i was adding up from post #2 for chamber neck id. a 308 bullet w/+ .003" (not sure if it's half the amount or total clearance) + .020" neck on brass.

 

[Lionel Boyd Johnson]

MagnumManiac: How do you do this: "To make the brass fit, it needs turning to be .014" at the upper end or .0135" at the lower end."?

 

[ntsqd]

MagnumManiac: How do you do this: "To make the brass fit, it needs turning to be .014" at the upper end or .0135" at the lower end."?

If I understand your question correctly, you need a tool like one of these:

Neck Turner Builder | Neck Turning Tools | Precision

Neck Turner Builder | Neck Turning Tools | Precision Micro Adjustable Neck Turner Tool & Best Neck Turning Tools for Accuracy

kmshooting.com

 

[Brathany]

Magnum is spot on with his advice. I found .0135-.014" neck thickness, measuring with a caliper just 1/8" inside the case mouth, provides .004" clearance when bullet is seated in a 7mm. OD=.312" and my chamber reamer print shows .316" at the case mouth. That's a total clearance of .004" with .002" radially. Another benefit to choosing your own reamer and specs. If you don't know the chamber spec, then a crude go/no-go test can be done to see if a bullet will still slide into a fired case. If the bullet slides in smoothly and drops to the bottom of the case, then there is clearance. If it doesn't fit into the fired case neck, then not enough clearance/brass needs turning.

Many 7mm cartridges have a chamber neck area cut to .316". The .308/30 cal family allows more clearance in the necks than 7mm. .342", .344" "No turn" reamers are popular for .308, with most factory chambers cut even bigger. Like, .008" clearance.

K&M turning hand held device with a cordless drill is what I have been using. 50 degree cutter. (Universal size)

.020" neck thickness is either rare, or doesn't exist. If you measure with the blade of the caliper too deep into the case it can give large reads. Just slightly pinch the first 1/8 into the case and take that measurement.

 

[ntsqd]

The tiny flat on the skinny face of the blades of a caliper will still result in a slight error in the neck thickness measurement. It is best measured with a tube wall thickness micrometer. Not because you necessarily need the precision level of a micrometer, but because with a round anvil it will not have a read error.

Like this: https://kmshooting.com/product/mitutoyo-micrometer/

 

[cajun]

Yes you really need a ball mic. Brass neck thickness is what it is. The big thing is it's even and you have proper neck clearance. Quality brass like lapua won't really need turning unless you have a tight neck chamber.

 

[Mike Matteson]

Following

 

[Jeffpatton00]

The thickness I prefer is based on numbers taken from the brass I chose, which just so happens to be accommodated by several brands, then I cut the chambers to suit. To make the brass fit, it needs turning to be .014" at the upper end or .0135" at the lower end.

What you're quoting, being .351"-.354" is probably close, but I would have a solid finished neck number FIRST to work off, no point cutting your chamber then discover it's too big or small. What brass has .020" thick necks?
The clearance is necessary only so the neck expands, if it doesn't and pinches the bullet, it will give you very high pressures.
When designing a chamber for custom applications, you need all dimensions first. SAAMI is very bad at making chambers too large, it's unavoidable because ALL brass has to fit it, but YOU can control this with a custom reamer.
Even a 'Match' chamber can be too large.

Cheers.

MagnumManiac, just a quick note to say how much I appreciate the thoughtful and well-seasoned advice you, Mike Matteson and a few others offer all of us on this forum. I'm a quiet observer on many posts, but fI'm here to learn, and the info you provide all of us, based on your experience, is invaluable. Thanks!

 

[Brathany]

Yes you really need a ball mic. Brass neck thickness is what it is. The big thing is it's even and you have proper neck clearance. Quality brass like lapua won't really need turning unless you have a tight neck chamber.

No, one really doesn't. +/- .00015 precision measurement isn't needed in this operation.

 

[cajun]

It's not the precision. Your trying to measure a curved surface with a flat object. The ball mic is made to measure tubing and round objects.