Checking cases after 4 Firings - Shooting Sports Forum


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Old 03-24-2019, 06:41   #1
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Checking cases after 4 Firings

Good read on what to look for after 4 firings and using a paperclip to see if the case head is about to separate.

RELOADERS CORNER: 4 Firings In, Part Two | Midsouth Shooters Blog
Glen Zediker

I’d always rather say it all at once, but the realities of tolerance, and space, sometimes mean I have to split a bigger topic into smaller installments. The “tolerance” part is how many pages you all are willing to scroll through!

This multi-part topic is when, and then how, to check after the progress of changes commencing with the firing on a new case. It’s the “progress of degeneration,” in a way of looking at it because the concern is getting a handle on when enough change in the brass has come about to require attention. Or abandonment. As said then, for me that’s 4 firings. That, as said last time, is when I might see changes that need attention. Also as said, that figure didn’t come out of a hat, but from my own notes in running my competition NRA High Power Rifle loads.

The areas most affected are the case neck and case head area. Case neck walls get thicker, and that was the focus last time. Well, the case head area body walls get thinner. Primer pockets get shallower and larger diameter.

As started on: Brass flows during firing. It expands, then contracts, and when we resize the case, it contracts, then expands (a little). This expansion and contraction makes the alloy harder over the entire case, but with more effect in areas of more expansion, and flow. Replace “hard” with its effect, “brittle,” and that’s a clearer picture. This increasing hardness influences its reaction to being sized or otherwise stretched. As with many metals, bend it back and forth enough times and it will break. It will also fail if it loses enough resilience, or thickness, to withstand the pressures of firing.

Case Head
When a case is under pressure during firing, the brass, like water, flows where it can, where it’s more free to move. Of course, the chamber steel limits the amount it can expand. The case shoulder blows fully forward and the case base is slammed back against the bolt face. There is, therefore and in effect, a tug on both ends — it gets stretched. The shoulder area is relatively free to expand to conform to the chamber, but the other end, the case head area, is not. Since that’s the area of the case with the thickest walls, it doesn’t expand “out” much at all. What it does is stretch.

The “case head area,” as I refer to it here, is the portion of the case above the web, which is just above the taper that leads in to the extractor groove. The “area” extends approximately an eighth-inch up the case body.
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Old 03-25-2019, 05:11   #2
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I'll say there's some characteristic unique to higher pressure cartridges. I've loaded brass a dozen times maybe more for my 625 steel plate revolver same for my GP100 target loads. would not do that with mu '06 though.
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Old 04-28-2019, 07:10   #3
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Mild loads will be easier the brass but like you said, the hotter high pressure rounds won’t hold up.
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Old 04-28-2019, 07:35   #4
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It is tough to reload for semi auto rifles, brass stretch is more noticeable. I see this with my mini and AR rifles and pending how hot the loads are.
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