Here's the senario. I recently attempted to anneal my first rifle cases (270 to be exact). I thought it went well. The next step I wanted to try was to neck size these cases with my full length die. In my Lyman Pistol manual, it showed to use some sort of marking medium to mark a few of your cases so you can set the die (I used washable marker). Well I got the die set to just size the neck, maybe a smidge high but it seemed if I went any lower I was going to hit shoulder. After I got this set, I measured my before and after headspace with my Hornady headspace gage. My after resizing headspace grew .002 for every case I measured (I did not measure every case). I found this to be extremely odd and it didn't seem right to me. Do I need to readjust my sizing die to prevent this or what? Every time I've used my headspace gages before, it's always been shorter after sizing.
This might be a stumper of a question.
- Thread starter varhunter
- Start date
CatShooter
New member
Originally Posted By: varhunterHere's the senario. I recently attempted to anneal my first rifle cases (270 to be exact). I thought it went well. The next step I wanted to try was to neck size these cases with my full length die. In my Lyman Pistol manual, it showed to use some sort of marking medium to mark a few of your cases so you can set the die (I used washable marker). Well I got the die set to just size the neck, maybe a smidge high but it seemed if I went any lower I was going to hit shoulder. After I got this set, I measured my before and after headspace with my Hornady headspace gage. My after resizing headspace grew .002 for every case I measured (I did not measure every case). I found this to be extremely odd and it didn't seem right to me. Do I need to readjust my sizing die to prevent this or what? Every time I've used my headspace gages before, it's always been shorter after sizing.
You did not say how far you went with the die, but when you say, " I got the die set to just size the neck, maybe a smidge high but it seemed if I went any lower I was going to hit shoulder.", then I get the impression that you are just a few thou from hitting the shoulder.
If that is the "case" (I made a pun
)... then this is what happened.
When you use a full size die, it starts to squish the body long before it hits the shoulder.
As the body is squished, the case gets a little longer (that brass has to go somewhere)... then when the case hits the die shoulder, the shoulder gets pushed back where it should be.
But if you neck size with a FL die, then the case gets squished, the shoulder moves forwards, but then you stop and don't finish the whole stroke, so the shoulder is left a bit forward.
It is normal and there is nothing to worry about.
You did not say how far you went with the die, but when you say, " I got the die set to just size the neck, maybe a smidge high but it seemed if I went any lower I was going to hit shoulder.", then I get the impression that you are just a few thou from hitting the shoulder.
If that is the "case" (I made a pun
When you use a full size die, it starts to squish the body long before it hits the shoulder.
As the body is squished, the case gets a little longer (that brass has to go somewhere)... then when the case hits the die shoulder, the shoulder gets pushed back where it should be.
But if you neck size with a FL die, then the case gets squished, the shoulder moves forwards, but then you stop and don't finish the whole stroke, so the shoulder is left a bit forward.
It is normal and there is nothing to worry about.
CatShooter
New member
Originally Posted By: varhunterGreat. So as long as the cases chamber I should be fine then.
Yup...
Yup...
RiverRider
New member
That's exactly what happens. You can make use of this to achieve a near perfect fit of the case to the chamber. If you can chamber the case after a partial FL sizing then you're good to go, but after several firings you might discover that you need to readjust your die so that you bump the shoulder back *just enough* so that undue force isn't necessary to close your bolt. I've set up my FL sizing dies using this method for years, but I don't measure a thing----I just go by feel. Be aware that turning the sizing die in a quarter turn can push the shoulder back around .018" which is quite a bit considering we're trying to get within one or two thousandths (we're talking headspace here). Getting the perfect adjustment is truly an exercise in patience.