On Fri, 06 Sep 2013 09:43:40 -0700, pyotr filipivich
wrote:

John B. on Fri, 06 Sep 2013 20:58:57 +0700 typed
in rec.crafts.metalworking the following:

Case diameter us shown as 0.278 and length is listed as 0.615 - .020".
Overall cartridge length is 0.860 min/.910 max.

The standard chamber is 0.2828 in diameter, and tapers to 0.2798 at
the front and is 0.0.638" in length. The cartridge appears to
headspace on a semi-rim.

I'm still a bit vague about the need for bullet length

I want to know this, because ...well "just because". Because I
want _all_ the details, because sometimes I get a wee tad too focused
on the details (I have been accused of trying to pick the fly specs
out of the pepper). Because there has to be some spec the bullet
makers use so that they know how little lead they can use in making
bullets. (Those hundredths of a gram add up.)
Because I am goofing about with the CAD software, and details are
everything.

And because I want a real drawing, complete with a seated bullet
in the cartridge. And the possibility (now) to include the bullet
itself in a separate drawing of it transiting the barrel.


If it is "just because" then likely getting pictures of various .25
cal pistol bullets and scaling the photograph will be sufficient.

I suspect that a bullet mold maker might furnish enough information,
see:
http://www.lymanproducts.com/lyman/b....php?entryID=1
Unfortunately Lyman doesn't seem to make molds for a .25 cal pistol
and a quick look didn't turn up any others :-(

On second thought, if you just want an outline of a loaded .25 cal
cartridge why not use the SAAMI drawings?


as it is never
really used in fitting a barrel or action. The action needs to be able
to handle the maximum cartridge length, the ejection port the maximum
case length, and the bullet is long gone down the barrel.

I've only seen Bullet length taken into consideration when deciding
on the rifling twist which in turn effects bullet rotation and
ultimately bullet stability.

The Greenhill formula , if memory serves.

Yes, but when you start driving .25 cal bullets at over 3,000 fps it
doesn't work quite so well :-)

--
pyotr filipivich
"With Age comes Wisdom. Although more often, Age travels alone."
--
Cheers,

John B.