Choosing Correct Bushing for Neck sizing

So I have some brand new unfired norma brass and the width of the loaded case neck is 0.3145"

By my reckoning I'd need a .313 bushing.

Does the neck wall thickness change much after firing?

Will I need a bit of a selection of bushings to chase the neck tension around as brass gets used?

Bit slack team, I cant help but others will surely know.

I believe that you measure your neck width on a loaded round and subtract .001" to determine correct bushing size?

Also, if your using Redding dies then you can use Wilson bushings that are tapered so you can invert them for a smaller bushing size.

Cheers fellas.

Found this which pretty much got me sorted.


http://panhandleprecision.com/reddin...roper-bushing/

I don't think the thickness changes, or at least bugger all. If your ordering some, order a size up or down as well. It took me three goes to get the right one. For whatever reason it just didn't work out as planned. The Wilson ones you can turn over, as there tapered, which is good if you want a bit more.
(All from memory, it's been awhile)

Quote:

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Originally Posted by Hayden C

I believe that you measure your neck width on a loaded round and subtract .001" to determine correct bushing size?

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You can subtract 001"-003" depending on how much neck tension you require. Remember too that a .001" reduction bushing is only .0005" neck tension and then you've got spring back. Most reloaders use a bushing .002"-003" less than a reloaded round.

The neck wall thickness does not change after firing. However, after you have fired each case several times, the spring back of the neck will alter as the hardness of the brass increases with multiple firings. So, the case will need a smaller bushing, than used initially, to create enough tension in the neck to hold the bullet consistently. I prefer a bushing smaller than the loaded round by 0.002 - 0.003" for hunting rounds because I don't want the bullets to shift in the cartridge case necks due to recoil while in the magazine. Different bullet designs may have slightly different diameters (same nominal calibre) due to the way different designs are manufactured which may affect the amount of tension/bushing size. It may be beneficial to turn the case necks down to a uniform thickness for use in the bushing die.

Quote:

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Originally Posted by rupert

The neck wall thickness does not change after firing. However, after you have fired each case several times, the spring back of the neck will alter as the hardness of the brass increases with multiple firings. So, the case will need a smaller bushing, than used initially, to create enough tension in the neck to hold the bullet consistently. I prefer a bushing smaller than the loaded round by 0.002 - 0.003" for hunting rounds because I don't want the bullets to shift in the cartridge case necks due to recoil while in the magazine. Different bullet designs may have slightly different diameters (same nominal calibre) due to the way different designs are manufactured which may affect the amount of tension/bushing size. It may be beneficial to turn the case necks down to a uniform thickness for use in the bushing die.

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OK cool, might grab a .312 as well.

I assume annealing would mitigate the work hardened brass issue a bit?

Quote:

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Originally Posted by 10-Ring

You can subtract 001"-003" depending on how much neck tension you require. Remember too that a .001" reduction bushing is only .0005" neck tension and then you've got spring back. Most reloaders use a bushing .002"-003" less than a reloaded round.

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1k BR guys are using .003 normally now. Do not go too light. You will have loose neck tension, bullets sliding back into the case etc.