culling brass via fat butt .....

A

alinwa

oft dis'd member
Here are some pictures which I hope will show how I can cull my cases for eccentricity using a fat-butted chamber and unhardened sizing dies. These cases were fired in a chamber which measures .007 larger than the unfired cases. I've included shots of both sides......the thin side to show just how far out a .007 bulge protrudes and the thick side to show how the die "scrubs by" clear to the base of the case. The rear of such a case is offset the full value of .007 from center.

Those cases which blow out concentrically are used for record rounds and the eccentric ones are used for sighters etc. I don't know that the eccentric ones are in any way less accurate, it's just something to do.

BTW, the "hideous bulge" is unnoticeable when using hardened dies. The unhardened die really scratches the surface of the brass to show the contour.


al
 

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Alinwa, some years ago, T.J. Jackson wrote an article in P.S. about
that exact thing. He found no accuracy issue there. That was
with rem 6br cases
 
Bob,

IMO there's no accuracy issue as long as the cases are firmly jammed for fireforming. Back when I was going thru my "jamming bullets and greazing cases" phase I fought with banana'd brass. I believe that the thin side (the one with the bulge) will stretch both radially and longitudinally without containment. By jamming the case, the lengthwise stretching action doesn't occur.

I THINK ;)

Anyway, my brass is now STRAIGHT!

al
 
The first picture shows a single case. This case is "flat" on the side showing......in other words when it's run into the sizing die the scratches show clear to the casehead, NO BULGE on this side of the case. (case was fired in a chamber that's .007 over the size of the virginal brass)

The second picture is of the "bulged" side of one case and the "flat" side of another.

A concentric case just has a tiny even bulge/ring around the web.


al
 
I'll try to find a clearer picture of the case with scrub marks clear down. Meantime, take my word for it......what looks like a bright streak of glare or a reflection is in fact the sizing streaks running clear down.

al
 
I presume many of you may have heard of the NECO concentricity gauge which has a "chord anvil" that reaches inside the case and allows indicating case wall variation. I bought one many years ago, maybe 20 now, and used it a bit.... that is until I discovered that at my level (a bit larger than "screamer" groups) I wasn't really gaining anything. Everybody's mileage varies of course.

It's still being made, and is a bit pricey now at $169 with indicator.... but if your alternative is shooting in an oversized chamber just to find case wall variation it might not be a bad investment in the long run..
http://www.neconos.com/shop/?shop=1&cat=10&cart=166268
 
Crow99

I've got one ;)

I'm a gadget-guy.......... I CHOOSE to run the fat butt, in fact I pay extra for it.

:)

al
 
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