I bought a 21st century neck turning lathe and just started. I'm doing some 7mm Rem Mag nosler brass. The concentricity is worse after I turn the necks. I'm running the brass over the expander mandrel that came with the lathe before I'm turning them. Any thoughts??
Neck turning
- Thread starter chetraguse
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- reloading
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Pretty neat article, but why does he full length size them, expand the neck, and then resize the neck? That seems like a ton of work. I realize that you have to expand the neck for the neck turning, but when I expand it with my mandrel it gives me the perfect neck tension. Maybe they aren't all like that?
dok7mm
Well-Known Member
What are you using to measure your necks?
Accuracy 1st guage
dok7mm
Well-Known Member
Are you measuring run-out or neck thickness? The two are very different. A ball micrometer or similiar tool is used to measure neck thickness, the target of neck turning.
Ball for thickness and accuracy 1st for runout. Just seems like can't get run out to be less than .0025 and maybe that's fine but I was hoping for less.
dok7mm
Well-Known Member
If you turned new brass, not fireformed in your chamber, there will be, sometimes, considerable run-out. Once it's fired in your chamber, the run out will be nil, if barrel/action alignment is correct. Then, you're GTG.
Mikecr
Well-Known Member
Chester, I believe you're doing everything right. After firing the necks there won't be any runout.
This is new brass
dok7mm
Well-Known Member
You're Golden!
Mikecr
Well-Known Member
It should be new for turning. No sizing, no firing and sizing, but new as it comes out of the box. Just expand with your turning system expander and turn (like you're doing). Preps are never complete, nor is any cartridge, until fire formed.
