Neck Turning 6bra - .268 Chamber

[cveg2887]

I am new to neck turning and need some guidance. I am using Lapua 6mm BR brass and turning the necks to .012 to fire form. I am turning just before the shoulder, so that I maintain the .004 crush for consistent fire forming. I tested 5 cases yesterday, and this seemed to work perfectly. I now would like to turn the necks again to their final thickness and just touch the shoulder. I am testing for the best clearance, so I'm not 100% sure on what the final neck thickness will be. I only have a bushing die for the 6BRA, and this only sized down a portion of the neck prior to expanding and neck turning again. Is there any issue using a bushing die for this process? I'm not seeing any non-bushing dies for the 6BRA. What process do you guys use to final turn your brass?

 

[JFrank]

I’ve only done this a couple times but I set mine for .0108 and only cut once then Fire Form. They come out pretty good. I use bushing dies and don’t worry about how much of the neck get sized, seems to work well.
My loaded round OD comes out about .265

 

[Bc'z]

I've done it 2 ways
I turn to the neck shoulder junction with a cutter that has a steeper angle than the shoulder.
I turned new brass , and after reading some folks saying fired cases are straighter and more true I turned a batch after firing.
I did not size any portion of the case before turning. The case was a little loose on the turning mandrel compared to new expanded brass.

Hell I can't shoot the difference.

 

[LRPV]

Get a full length die to size the neck all the way to the shoulder OR get an oversized turning mandrel that fits a fired neck to do the final turn. As long as your chamber is good and your necks don’t get dinged on the way out, a fired case will be as straight as it gets.

 

[LCazador]

When you put the case through the expander turning mandrel, the neck is going to be consistent all the way down to the shoulder even though you only sized part of the neck. Full length size first with bushing die or body die then trim to a uniform length. This uniform length will make your cut into the shoulder consistent. I don't think you have enough clearance if you turn necks to .012", that gives a loaded diameter of .267". In my experience this limited clearance can produce undue stress on the brass. Turn to .0115", this will give you .002" clearance and a loaded diameter of .266". For a final cut I make a .0002" cut. I seat bullets into the lands to solidly hold the cartridge base onto the face of the bolt and use a moderate load for fireform. Keep in mind that most new cases will be shorter than your chamber so trying to headspace off the shoulder is not a good idea. I would also suggest the you take a headspace measurement on your new brass, I use a barrel stub made with the chamber reamer for this dimension. Also take a head measurement of the new brass so you can monitor case head expansion and pressure.
Try all this with a few cases.