From: toby@stein2.u.washington.edu (Toby Bradshaw)
Subject: Re: What is 30-30 Ackley Improved?
Organization: University of Washington, Seattle

In article <27298u$rl5@elroy.jpl.nasa.gov>,
M Lang <Lang@inst-sun1.Jpl.Nasa.Gov> wrote:
#- I understand that the accuracy depends largely on barrel, chamber,
#  action, bullets and brass quality etc... but if the cartridge shape
#doesn't
#  have a lot to do with its accuracy, how come one cartridge is more
#  successful than the other (for example, 6 PPC in benchrest)? Does the
#  cartridge design has something to do with it?

Frankly, nobody knows.  The PPC came along at a time when several
major advances were made in BR rifles -- synthetic stocks, glue-in
bedding, etc.  PPC brass has always been very, very good as far as
case wall thickness and concentricity go; much better than average
U.S.-made brass.  Good brass is vital to shooting tiny groups.  The
PPC powder column is short for the case capacity, and the head is
real thin (short flash hole).  This has been reported to improve
the uniformity of ignition.

Other short cases, like the Remington 6BR and 6mm Wasps based on
the Federal .30-30 American case have been made to shoot as well
as the best PPCs -- it is harder to find good brass, though.  The
standard .222 will shoot with the PPCs at 100 yards, but are a
little too wind-sensitive to win consistently at 200.  Mostly,
everybody shoots a 6PPC because its the path of least resistance.
Reamers are held very close to the minimum brass dimensions, and the
brass is held to unbelievably tight tolerances.  Note that of
10 Lapua .220 Russian cases tested by Jim Borden and shown in
Precision Shooting, none (or mabe one) ran out as much as 0.001.
I checked a couple dozen Lapuas for my 6PPC and you'd swear the
dial indicator was broken, because the needle doesn't move.  Try
that with even the "best" Rem 6BR brass -- approximately 75% culls.
Of course, a BR barrel can be worn out with about a dozen cases,
so we can afford to go to some length to get good ones.

-Toby Bradshaw
toby@u.washington.edu