Neck sizing for a wildcat

[MontanaRifleman]

Makes sense, thanks for the answer.

Mark

[Forester]

Originally Posted by Mikecr

Turning mandrel fit.

When he sizes down the brass will gain 3-4thou in thickness and get wild.
Then he'd have to anneal and use every bushing and mandrel in the box trying to get a workable fit with his turning mandrel. Bad fit, bad turn.

On the other hand, It would be easy to turn a piece at 30cal, a few thou under desired, size down, & check thickness with a ball mic(or seat a bullet & measure neck OD).. Tweak the turn depth and do it again.
It's always trial and error with a turning setup. So I suggest he keeps it simple as possible, by fitting and turning the brass while it is in a normal state.

I can see the benefit of a quick clean up pass at 30 cal. to hopefully have the brass size down in a more uniform way. But doesn't the expander mandrel have more to do with getting a good fit to the turning mandrel than anything?

If I size down to bullet diameter, then use a sinclair expander to set the neck ID just larger than the turning mandrel then it should turn fine right?

After working the brass this much I was planning to anneal it anyway, should this be done before or after neck turning?

I ordered 150 pieces of Norma 300WSM brass, Dies and a small fortune in bushings so I should be getting started on this next week.

[Mikecr]

Originally Posted by Forester

doesn't the expander mandrel have more to do with getting a good fit to the turning mandrel than anything?

Yes, I hope I haven't somehow contradicted this.

Originally Posted by Forester

If I size down to bullet diameter, then use a sinclair expander to set the neck ID just larger than the turning mandrel then it should turn fine right?

Nobody loves the Sinclair system better than I. And it might work. But you should plan for what you need.
The 7WSM's neck is shorter than the 300WSM's by .054". Thats dangerous headspacing, so you'll need a false shoulder for fireforming.
This is good with the turning at 30cal plan. No need to turn up onto shoulders as .054" of the 30cal neck is going to end up shoulder anyway(eliminating any possibility of doughnuts).
And then you can just partial neck size for snug chambering.
You won't need to re-anneal Norma with a single direction sizing from 30cal to 28cal. Don't worry about it one way or another.

[Forester]

Originally Posted by Mikecr

Yes, I hope I haven't somehow contradicted this.

Nobody loves the Sinclair system better than I. And it might work. But you should plan for what you need.
The 7WSM's neck is shorter than the 300WSM's by .054". Thats dangerous headspacing, so you'll need a false shoulder for fireforming.
This is good with the turning at 30cal plan. No need to turn up onto shoulders as .054" of the 30cal neck is going to end up shoulder anyway(eliminating any possibility of doughnuts).
And then you can just partial neck size for snug chambering.
You won't need to re-anneal Norma with a single direction sizing from 30cal to 28cal. Don't worry about it one way or another.

I am not fireforming 300wsm into 7WSM, I am building a 7-300WSM wildcat. In other words, a 300WSM, necked down to 7mm, no change in shoulder location. I won't have all that headspace because the reamer will be cut as though it were a 300, and the neck cut to something like .314 for the .284 bullet and .014 necks.