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Old October 20, 2012, 03:13 PM   #1
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inside neck sizing 5.56 and 223 ?

When sizing 5.56 and 223 cases how many of you guys use the inside neck sizing rod and how many remove it ?
I think I read some where that removing it improves accuracy or I maybe misread it.
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Old October 20, 2012, 04:23 PM   #2
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In any cartridge, the standard sizing die uses the expander because the maker doesn't know where in the tolerance range the thickness your brass will have at the neck. His objective is to make the inside diameter of the necks all identical to give you the same press fit interference and resulting bullet bullet pull among them all. But when you size a neck from the outside, a thick neck wall makes a smaller neck ID and a thin neck wall makes a bigger neck ID. So the only way to keep them all the same is to size them all enough so the thinnest neck will still grip the bullet well, then use the expander to adjust the others.

The problem that arises from that approach is the expander has a tendency to pull the whole neck a little off axis, as the Hornady die in this video does (and this applies to all makes of standard sizing dies, and not just Hornady). To avoid that, you can use a Lee Collet Die, as in the video. You can also get a die that uses neck bushings, then sorting all your brass by neck wall thickness and using the right bushing for each thickness.

You may also, as you described, simply remove the expander from the die or, if you have your decapping rod dependent on the expander, swap in an expander for the next smaller caliber. There are still issues with this, though. One is you will now be using the bullet as its own expander. Pushing down to expand rather than pulling up does seem to be less prone to bending the neck, but it's not necessarily going to be zero bending if the push is hard or if the bullet isn't being pressed in perfectly straight.

A good workaround is to buy the Lyman M die which expands by pushing straight down, the leaves a small step in the mouth so the bullet sits upright on its way into the seating die. This helps straightness significantly. It also tends to stop the sharp edge of a freshly trimmed case mouth from shaving small rings of gilding metal off the bullets. Chamfering alone doesn't solve that completely. The only limitation with the Lyman M die is that you will have to set the crimp shoulder on your seating dies just low enough (or getting a separate taper crimp die is even better) to iron the step back out again.
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