Keeping necks concentric

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RedSkyFarm

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I'm a fairly new reloader. I've read from time to time on the forum of neck sizing vs. full length/partial full length sizing. Appears that most at least partial full length size to 1) bump the shoulder back .001-.002", and 2) to keep the neck concentric. Please correct me if I'm not right. My fired cases are .006" longer at the shoulder than a new case (measured with a comparator). I'm getting better accuracy from NS cases than the partial FLS cases. My neck sized cases are chambering fine and haven't had an issue closing the bolt or having one stuck in the chamber. My question is: How does a NS die keep the neck concentric with the body of the casing? I am using standard RCBS dies at this point. I here good reviews on the Lee collet dies. Does the Lee die function differently than the RCBS die to keep the necks concentric? Thanks for any input.
 
RedSkyFarm said:
I'm a fairly new reloader. I've read from time to time on the forum of neck sizing vs. full length/partial full length sizing. Appears that most at least partial full length size to 1) bump the shoulder back .001-.002", and 2) to keep the neck concentric. Please correct me if I'm not right. My fired cases are .006" longer at the shoulder than a new case (measured with a comparator). I'm getting better accuracy from NS cases than the partial FLS cases. My neck sized cases are chambering fine and haven't had an issue closing the bolt or having one stuck in the chamber. My question is: How does a NS die keep the neck concentric with the body of the casing? I am using standard RCBS dies at this point. I here good reviews on the Lee collet dies. Does the Lee die function differently than the RCBS die to keep the necks concentric? Thanks for any input.
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Yes, the Lee Collet Neck Die just has a straight mandrel, and as the case goes up into the Die, it has four "finger" (for lack of better words) that presses the case against the mandrel. I use a Lee Collet Neck Die in my process to make my match rounds.

The biggest difference is there is no expander ball going through the neck...that's normally what induces runout.


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Thanks for the information. Watched the video. I see how it works. Still have a question on bump sizing when the time comes when bumping the shoulder back will be necessary. I've tried bump sizing on some scrap cases with my standard RCBS FL die. I am not able to bump the shoulder back at all. If fact, it grows. I've run the case up until the shell holder bottoms out on the die and the shoulder never gets touched. I believe the brass is flowing up the case, making the measurement from the head to the datum longer. You are using the Redding "body" die to bump the shoulder back. Is there another alternative other than the Redding dies?
 
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You can either file down your shell holder or I believe Redding makes shorter shell holders which would allow your sizing die to set your shoulders back.
 
DAVID NANCARROW said:
You can either file down your shell holder or I believe Redding makes shorter shell holders which would allow your sizing die to set your shoulders back.
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They do. I believe it's the Competition shell holders. They go down in .002" increments.

You still want the Redding Body Die. I can't recall off the top of my head if there's another Die like it out there.


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Backwards

The Redding Competition Shell Holders increase the height, not reduce it. The assumption is that will be needed for a chamber whose headspace is greater than minimum. If you can't touch the shoulder at all, that suggests a short chamber or an oversize die. You can have the mouth of the die ground down to fit your chamber. Many match shooters have done that. You can also try Mr. Guffey's method of removing the decapping pin and slipping an automotive feeler gauge between the case head and bottom of the shell holder.

Normally a case's head-to-shoulder length is increased as the sizing die narrows it, and that is what gets pushed back. If this is not happening, you may be one of the rare folks who actually needs a small base die. They are narrower than standard and may set the brass correctly for you, too.
 
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