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Old May 13, 2012, 03:22 PM   #1
JRLSH
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Help with Headspace

I would like some information on reloading for .50BMG. Headspace! I have been reading about headspace and its importance and am somewhat confused. Headspace, as I understand it, is the distance from the middle of the shoulders of a case(or where the shoulders sit against the breech of the barrel in the chamber) to the base of said case. The shoulders sit on the chamber walls of the breech of the barrel. So when I full length size the cases I measure the length of my trimmed cases and all are within specs, 3.910, and the shoulders look and measure just as the specs in the manual say they should. My question is this: If I have shot a new round in my gun and have now fireformed the case to my guns breech do I still need to worry about headspace? Or is the headspace now set for my gun? These newly fired cases are going to be worked on a neck sizing die only and not on a full length sizing die so would headspace still be an issue? Thanks to all in advance.
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Old May 13, 2012, 04:34 PM   #2
PA-Joe
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Are you using a bolt action or a semi-auto? If bolt you are correct, the fireformed cases should fit your action if only neck sizing. However, you will reach a point where they will not chamber and must be FL resized. In a regular caliber this may be three to five firings. With the 50 I wouldn't be able to tell you how many before you will have to FL resize. If a semi you may have to FL resize each time since the case will stretch as the action is moving.
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Old May 13, 2012, 04:47 PM   #3
mehavey
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Quote:
If I have shot a new round in my gun and have now fireformed the case to my guns breech do I still need to worry about headspace? Or is the headspace now set for my gun? These newly fired cases are going to be worked on a neck sizing die only....
As above (if you are firing a bolt action), the case is now custom fire-formed to the chamber's headspace dimensions. Necksizing at this point will preserve those custom dimensions, although the case brass will very gradually flow forward after repeated firings to require you set the shoulder back again.

You'll know 'when' as the loaded cases will give you more & more "feel" on closing. When that feel gets truly noticeable, resize again.
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Old May 13, 2012, 10:38 PM   #4
Bart B.
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JRLSH comments:
Quote:
Headspace, as I understand it, is the distance from the middle of the shoulders of a case(or where the shoulders sit against the breech of the barrel in the chamber) to the base of said case.
That dimension on a case is usually referred to as case headspace. In the barrel's breech end, it's commonly called chamber headspace. When a new case is first fired, its case headspace is typically 1 or 2 thousandths shorter than chamber headspace; the case expands hard against the chamber walls and bolt face then shrinks back a tiny bit. If one wants to neck only size that case, it's in perfect dimensions to do so as it's a good fit to the chamber for that sizing process. But as Mehavey says, that shoulder will move forward every time the case is neck sized and fired; it shrinks less and less each time. Eventually, it binds up when the bolt's closed chambering it. And if the rifle's bolt face isn't squared up with the chamber axis, the bolt binding up on the case head differently for each shot will really hurt accuracy.

I strongly suggest full length sizing your fired cases. Use a gage to measure case headspace; first on the fired case to see what it reads then after full length sizing it such that the shoulder's set back about 3 thousandths. Adjust the die height in the press to do this. This prevents any binding of the sized case against the bolt face when its chambered. Anytime the bolt binds when chambering a round, even the slightest amount that barely noticed, accuracy sufferes. While neck only sizing of fired cases was popular in benchrest disciplines, they've been full length sizing their cases more and more the last couple dozen years. Full length sized cases center just as perfect as neck sized ones when they're fired anyway.

Last edited by Bart B.; May 13, 2012 at 10:44 PM.
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Old May 18, 2012, 04:49 PM   #5
JRLSH
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My thanks to all

To all who responded, my heartfelt thanks. I sincerely appreciate this board and all who generously give of their knowledge to help folks like myself keep from blowing themselves up. (LOL) No, really, thanks guys for your help. Happy Shootin....
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