[bigcim]

When neck turning how much of the neck should you turn

[ranger335v]

Bottom line is, cut as much as you want to reduce the thickness variation that offends you.

In the real world, with factory rifles and their loose chambers, it is accepted practice to cut perhaps 60-80% of the circumference and live with the remaining variation.

Turning necks for factory rifle ammo is almost like shoveling beach sand against the surf, it really doesn't accomplish much. I do it anyway.

[jibjab]

I turn my case necks as little as possible, I do it mostly to cull out bad brass. A tubing micrometer is the best way to get a average neck wall thickness.
Load a small batch with turned necks and with out, shoot two targets side by side alternating the rounds and see if it makes a diff. :)

[bigcim]

let me clarify I meant how far down the neck 1/8'' ,1/4'' all of it?

[jibjab]

I guess reloading does occupy more than one dimension :D I turn my cases down to the shoulder, or down to 1.712" from the base if turning the neck on .308 win. brass.

[Walkalong]

Neck turning is not necessary most of the time. Do you have a tight necked chamber? Are you reforming brass?

If you just want to make the necks uniform then turn them until about 90 % of the necks, on average, are trimmed when you hit your target neck thickness. No need to trim off any more as it can be detrimental.

If you turn them, turn them until you just touch the shoulder like jibjib said.