Multiple neck turns on the same brass?

[jlow]

I recently started to neck turn my LC09 223 brass to get more consistent neck tension.

The thing that surprise me is after neck turning the case to size and using the case in multiple firing, I find that if I run the case again through the neck turner, it take more brass off the complete neck with the turner left on the original setting.

Is this because firing the case somehow pushes more brass down into the neck? If this is the case, should one make passes everytime the case is fired? What is the right thing to do?

 

[turbo54]

Re: Multiple neck turns on the same brass?

Yes, the case neck gets thicker from firing and sizing. Brass flows.

The only reason to neck turn a case more than once is if it no longer has adequate neck/chamber clearance, which is RARELY EVER an issue on a factory chamber - or even a chamber cut to SAAMI specs.

 

[jlow]

Re: Multiple neck turns on the same brass?

Thanks! Appreciate the advice.

 

[Jeffvn]

Re: Multiple neck turns on the same brass?

+1 yes you eventually will need to turn one more time if you want to keep it all to spec. I was a bit surprised to find this myself when I was diagnosing some vertical in my 7WSM reloads on my F-Class rig. My rig runs a 0.013 neck, and a .313 neck for my 7 WSM.

I trim regularly, but never went back and checked neck thickness. oops some had grown by nearly 0.0015, which is a bunch in a chamber with a grand total of 0.003 clearance. Anyway, I turned it all again, and back to normal. It was a wake up call that I need to keep on top of it.

JeffVN

 

[jlow]

Re: Multiple neck turns on the same brass?

Thanks for your response, I find your comments extremely interesting the reason being that apart from finding that there is more to turn in this brass that has been previously turned and then fired multiple times, I am also finding that I am getting consistent vertical stringing in rounds loaded with this brass.

Here is a good although not isolated example. The group was generated with 10 rounds of 77gr Nosler CC, loaded in LC09 brass neck turned once but previousely fired three times. Powder is Varget 24gr. As you can see, the horizontal spread is 0.478 MOA but the vertical spread is more like 1.645 MOA.

Data analyzed with OnTargetCalc.com software.