Neck Thickness Estimate

[mikecr]

When it comes to up/down cal changes, it seems pretty much trial & error to find resultant neck thickness.
I turn NEW necks trial & error before up or downsizing to a different cal. This, because it is far easier to turn new/unsized necks.

But it just dawned on me that this thickness problem should be easy to calculate.
So I just put a spreadsheet together to do it.
Basically, I'm determining brass area for an entered cal & measured .xxx thickness. Given that brass area will not change with up/down sizing, a new neck diameter with the same brass area must be at .yyy thickness.

 

[dgeesaman]

Seems straightforward and handy. Does it agree with measurements?

 

[mikecr]

Do to things going on, my reloading bench is down for a while..

 

[Bill K]

I like to keep it simple, so I will just run my brass through a neck trimmer to take down the high areas, but also keep the neck thickness at .012 to .013, this seems too work well for me on all my cases and sure aids in getting maximum use out of each case.

 

[mikecr]

Bill this is for up/down sizing thickness estimation.
For example:
I start with 25wssm cases, neck thickness at 19.5thou.
I need to turn necks at 25cal, before upsizing to 26cal, so that the necks come in at 13thou thickness -with that upsizing.
This was trial & error for me before, but this spreadsheet tells me to cut native necks to 15.2thou thickness, and when I neck up to 26cal I will have necks at 13thou thickness.