Fitch
Well-Known Member
I started a new thread to avoid hijacking the one on case length.
I always make sure my brass is under SAAMI max. I understand completely why and how having long brass can blow up a gun. So I measure it and trim as necessary. No problem.
Unlike most of my other brass, my .30-06 brass (1953 Win M70) grows like corn on a warm summer night. I can barely go two firings with out trimming and I usually trim it every time taking off .005" to .009".
I've adjusted the RCBS full length sizing die (not an X-die) to bump the shoulders only .002" near as I can measure.
So when the RCBS X-Die was mentioned in the other thread I went looking for it, but before buying one I'd like to "know" it will extend case life which means I need to know how and why it works.
So far what I've been able to find out is that it acts like a short chamber and compresses the brass back to length in some fashion. Try as I might (trust me on this, it's easy to get me to buy a new tool!) I can't get my head around why that would extend case life.
As I understand it, brass grows mostly near the base at or just above where the web in the case head thins to wall thickness. There is a good illustration of that on Varmint Al's web site, and I see it when I check brass with my RCBS case checker which can give me a profile of case wall thickness. I bought it because I was getting suspicious of my .22-250 brass.
My .22-250 brass, before I rechambered the rifle, grew, which resulted in measurable case wall thinning in the form of a trough, ring, around the case just above the base. When I saw it getting to be .002" deep I pitched the brass.
Back to my questions:
1) How does restraining the case neck axially with the equivelant of a short neck chamber in the die do anything about the thinning just above the web?
2) If it doesn't do anything about the thinning above the web, how can it extend case life?
3) Brass isn't a compressible fluid. The case has to act something like a balloon full of water - squeeze it here, it gets bigger there - it's always the same volume, just a different shape. If the case stretches near the web, where does the extra length (material) go if the brass isn't longer after it's sized?
Thanks
Fitch
I always make sure my brass is under SAAMI max. I understand completely why and how having long brass can blow up a gun. So I measure it and trim as necessary. No problem.
Unlike most of my other brass, my .30-06 brass (1953 Win M70) grows like corn on a warm summer night. I can barely go two firings with out trimming and I usually trim it every time taking off .005" to .009".
I've adjusted the RCBS full length sizing die (not an X-die) to bump the shoulders only .002" near as I can measure.
So when the RCBS X-Die was mentioned in the other thread I went looking for it, but before buying one I'd like to "know" it will extend case life which means I need to know how and why it works.
So far what I've been able to find out is that it acts like a short chamber and compresses the brass back to length in some fashion. Try as I might (trust me on this, it's easy to get me to buy a new tool!) I can't get my head around why that would extend case life.
As I understand it, brass grows mostly near the base at or just above where the web in the case head thins to wall thickness. There is a good illustration of that on Varmint Al's web site, and I see it when I check brass with my RCBS case checker which can give me a profile of case wall thickness. I bought it because I was getting suspicious of my .22-250 brass.
My .22-250 brass, before I rechambered the rifle, grew, which resulted in measurable case wall thinning in the form of a trough, ring, around the case just above the base. When I saw it getting to be .002" deep I pitched the brass.
Back to my questions:
1) How does restraining the case neck axially with the equivelant of a short neck chamber in the die do anything about the thinning just above the web?
2) If it doesn't do anything about the thinning above the web, how can it extend case life?
3) Brass isn't a compressible fluid. The case has to act something like a balloon full of water - squeeze it here, it gets bigger there - it's always the same volume, just a different shape. If the case stretches near the web, where does the extra length (material) go if the brass isn't longer after it's sized?
Thanks
Fitch