Neck turning questions

[Cbmax]

Hello,

I have been reloading for 15 + years. I just had a precision rifle built in 6.5 Creedmoor and decided that I wanted to turn my case necks for uniformity and improved accuracy. The rifle does not require neck turning due to a tight chamber. I am taking this step to see how it improves accuracy.

Here are the current steps I take in this order:

1) Starting with new brass
2) Full length size the case using a bushing die. The bushing is in the die during this step and I let the bushing have a slight amount of play per Redding's instructions.
3) Trim cases to exact same length
4) Chamfer / de-burr
5) Uniform primer pocket
6) Run case through an expander die that came with neck turning tool.
7) Neck turn the case using a 21st Century Shooting lathe (I use imperial wax as a lubricant on the mandrel and the outside of the neck)
8) Use fine steel wool to polish out any rough spots especially near the shoulder.
9) Neck size only
10) Prime case
11) Pour powder
12) Seat bullet

The issue I am running into is that after I neck turn, it appears that the rim of the case mouth is uneven. I have adjusted the cutting length so that the blade just touches the shoulder. I clean the blade with a tooth brush when it is excessively dirty. I think I am using the right amount of lube, but maybe I am not? I don't think I am taking too much material off the brass, but maybe I am? Using a ball micrometer, the neck thickness of the brass averages somewhere between .014 and .015 inches. I am turning the brass to get the thickness down to .0135.

In an attempt to fix the case, I started re-trimming the case to square up the case neck rim.

Am I doing something incorrectly or is it normal to re-trim brass after neck turning and before resizing the neck only?

Thanks for any advice you can offer!

Chris

 

[Supersubes]

Could what you’re seeing be an illusion based upon an uneven outside chamfer? I wouldn’t outside chamfer till after the turning is done, and the inside...just enough to get the case on the mandrel(if you had an inside burr remaining from the trim) . Having said that, I hate neck turning, and avoid it personally. I’ve used it in the past on sub caliber cartridges, which take some work to get the velocity spreads down. You’re using lapua brass, yes? Are you struggling with high Es/sd?

 

[Supersubes]

What I meant by the illusion...

If you outside chamfer a trimmed case, you end up with something that looks pretty even. If that case has a thick wall on one side, and you neck turn it, you remove more of the chamfer from the thick side(because there was more depth of cut there), giving the chamfer a wavy uneven appearance.

 

[ZiaHunter]

When turning new brass I start with the expander, trim to length then turn. I wouldn't recommend using a bushing die since it only sizes a portion of the neck and best to use a standard FL die with the expander removed if you want to size prior to turning. It is important that neck length is uniform prior to turning to get a consistent cut into the shoulder. Using a Giraud trimmer indexes of the shoulder so will provide a uniform neck length. I lube the inside of the necks prior to turning to prevent galling and periodically dab a bit of sizing wax on the turning mandrel. I have gone to carbide mandrels since they seem to provide a more consistent neck wall thickness. I turn all of my brass for my F Class rifles and use the 21 Century turning tool with the lathe attachment. Turns brass quickly and accurately and can contribute to consistent neck tension if done properly which combined with precise charge weights can reduce vertical dispersion at longer ranges.

 

[Cbmax]

Perhaps it is an optical illusion. I will try chamfering after the neck turning has been done. That makes a lot of sense! As for the bushing die, I thought it resizes the entire case if I have it set up to do so. I bought 50 pieces of new Hornady brass and 100 pieces of new Lapua brass. I figure that I would practice my neck turning skills on the Hornady brass before moving to the more expensive Lapua brass if it even needs neck turning. Thanks for the advice and I will post pictures of my results shortly!

 

[Cbmax]

Here is a piece of brass that I just prepped. It seems like this one came out better. I tried to run the case through the expander die without performing an outside chamfer (debur), but the case didn't want to go into the die. I did tweak my full length resizing die. Maybe that was the trick? Maybe I need to adjust my cutting length to go slightly further into the shoulder?

 

[ZiaHunter]

For expanding the neck prior to turning best to use an expander mandrel matched to the turning mandrel. The expander mandrel is tapered at the end allowing it to enter the case neck, Turning looks fine and you may want to cut a little further into the shoulder. Main reason for cutting into the shoulder neck junction is to minimize the formation of doughnuts.

 

[Cbmax]

Thank you ZiaHunter. I am using a matched expanding mandrel and I adjusted my cutting length.