Neck Turning of cases

[BC]

I have a couple of questions on neck turning of the cases.

1) Does neck turning weakens the neck due to the reduction of the thickness?

2) If neck turning is done to even out the outside of the case then are we assuming that the inside of the neck is perfect?


Thanks


BC

[shooter mcreid]

Part of the neck turning process is to size the inside of the neck with a mandrel first. This step aims to push the excess to the outside of the case ready to be trimmed off, effectively making the inside diameter close to perfect. During the cutting process an arbor helps align the case. I hope this answers point two?

[RAVEN]

1) Does neck turning weakens the neck due to the reduction of the thickness?

NO
provided you are only removing enough neck brass to uniform the necks

poor case chamber fit does more harm to the brass symptoms are split necks & case head separation.

2) If neck turning is done to even out the outside of the case then are we assuming that the inside of the neck is perfect?

any imperfections are knocked to the inside after the first firing I would also use a donut cutter for when re-turning after the first firing.
RB

[Fergus Bailey]

1) Does neck turning weakens the neck due to the reduction of the thickness?

No. Your aim with neck turning is only to take off a minimal amount of material to give you a consistent round. The reamer should be ground with the dimensions of the brass, bullet and total clearance in mind, though unfortunately batches of cases do vary so thats another wildcard to manage in the process.

2) If neck turning is done to even out the outside of the case then are we assuming that the inside of the neck is perfect?

As noted, you need to use a case neck expanding mandrel to push any irregularities to the outside neck where the case neck turner can cut them off.

Also note that it is important to buy an expanding mandrel that matches your turning arbor. If the two pieces do not match up properly, the cases can be very hard to turn and can generate heat which will lead to inconstant neck thickness, or the necks will be a little loose on the turner, which will also lead to inconsistent necks.

[aaronraad]

I have a couple of questions on neck turning of the cases.

1) Does neck turning weakens the neck due to the reduction of the thickness?

2) If neck turning is done to even out the outside of the case then are we assuming that the inside of the neck is perfect?


Thanks


BC

I'd have to disagree with the previous posts on 1). Neck turning does weaken the brass. Remove too much and the neck will split.

Theoretically cases produced to SAAMI or CIP will have the correct thickness to suit the SAAMI or CIP chamber. Deviate from this and you're on your own so to speak.

Remember the reason brass is such an excellent cartridge material is that it will expand and spring-back. If the neck wasn't 'weakened' it wouldn't expand to release the bullet, seal the chamber and then spring back slightly (within it's elastic limits), hence the wall thickness at the neck is significantly less than the case head.

Case in point - the 5.6x57mm RWS was designed with a 'thick' neck to handle specialised adaptor cartridges. Reloading fired cases was significantly more difficult because of the thicker neck design. The necks work hardened quicker and if they weren't 'thinned' or annealed splitting would also occur.

It's a balancing act.

[RAVEN]

I'd have to disagree with the previous posts on 1). Neck turning does weaken the brass. Remove too much and the neck will split

Aaronraad as with all things excessive. Removing too much brass of course will weaken the neck I would have thought that would be a no brainer

Humm after 10 of thousands of rounds on neck turned brass to fit my tight neck chamber I haven't had not one failure (split neck)

But had plenty on a standard SAAMI Rem Mag chamber with factory brass.
I would only turn brass to fit a specific chamber neck if you are trying to remove some variables at very least a 50% clean-up will improve your neck tension.

No one can mass produce a product like cartridge brass to our exacting demands.
RB

[DaveMc]

A side benefit of turning is the neck to chamber fit can be designed so there is minimum expansion and then sizing resulting in much longer neck life. In practical terms this often means turned necks last longer than a lot of unturned if designed to fit the chamber with small neck clearance. If however you turn the necks and have a no turn chamber (or factory) and end up with excessive clearance then the effect can mean reduced neck life.

A no turn (or even worse - factory) chamber has to be designed to allow for a few more variables and generally a bit more clearance.

If you have small (say <4 thou for arguments sake) clearance and minimal turning then you can expect a very good case life result.

[BC]

Hi

Thanks for you answers to my two questions. From what you say, it looks that it is a more complex procedure than what I see on youtube.


BC

[RAVEN]

[RAVEN]

No not at all
just educate yourself about the process first http://www.6mmbr.com/index.html
is a good place to start