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Discussion Starter · #1 ·
All,
I am inquiring about 9mm case sizing as I seem to be seeing something I have not encountered with another cartridge that I reload. (.45)
Details:

Dillon 9mm dies (sizing, seating and crimp)
Dillon 550b progressive reloader.

After sizing a 9mm case, the mouth of the case measures .376 give or take
.001-002. The case head measures .386, again give or take .001-.002.
Does this sound/look normal after sizing? Once the bullet is seated and the final taper crimp is applied, the case has a distinct "hour glass" shape to it, quite noticeable when held up to the light and a white background. Is this normal? Doesn't look like a factory round which is why I am asking. What could be causing the hour glass shape of the case to occur? I have taken the die out of the tool head and inspected it, nothing abnormal seen. The carbide insert is not damaged. The die is screwed all the way down to touch the shell plate and backed off a quarter of a turn per Dillon instructions.
Thank you for your replies.
 

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Sounds normal and good. The 9mm Luger is a tapered case. Factory rounds have a "straight" line to the sides, even though the case is tapered. The hourglass appearance is also good for sized cases since it indicates that you have good neck tension on the bullet to help reduce/prevent setback.
 

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Once the bullet is seated and the final taper crimp is applied, the case has a distinct "hour glass" shape to it, ... What could be causing the hour glass shape of the case to occur?
By design, the sizing die reduces the case diameter. When the bullet is seated it expands the case causing the hourglass shape. As mentioned, this is a good thing as it provides additional neck tension helping to reduce bullet setback.
 

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If it chambers and shoots and the dimensions meet SAAMI, it seems OK to me.
I don't care if it has that visual coke-bottle look. Some factory ammo has it too.
 

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Discussion Starter · #6 ·
Thank you for the replies everyone. I looked at some factory rounds and sure enough, there is a slight taper to the cartridge. Never noticed it before. Learn something new everyday. All of the rounds that I have loaded and shot have been flawless.
 

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I've noticed that different sizing dies "shape" the case differently. My finished rounds using a Lee carbide sizing die pretty much look straight walled (although there is a slight, measurable taper) with, sometimes, a small band/bulge where the base of the bullet rests inside the case (depending on brass and bullet).

A Redding non-carbide/steel die (don't ask, yard sale find ... and I actually like them) actually sizes to almost a funnel shape. More sizing at the mouth to about 1/3 down and tapering toward the rim from there. Actually provides better case neck tension and more of an hour glass shape when loaded (compared to the Lee).
 
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