RCBS Gold Medal Dies - Manual (Page 10)

During firing, cases expand to fill the chamber or your
firearm, after the bullet has left the muzzle, pressures
drop and the cases shrink slightly to allow extraction from
the chamber. The case, with some shrinkage, is now an
accurate representation of the chamber of your firearm.
This initial expansion of the case can change headspace
by .005" or more. Rather than fully resizing the head-
space and case dimensions back to SAAMI minimum,
you can simply "bump" it back a few thousandths to
insure chambering. This also gives you a more efficient
use of the pressures created under firing by not having
the case expand as much.
To set the Gold Medal Full Length Sizer die to "bump"
headspace, with the shell holder in the ram and the ram
at its highest point, screw the Sizer die down until it con-
tacts the shell holder. Back the die up 1/2 turn and
secure with the lock ring. Take a properly lubricated case
that no longer chambered in the firearm and size it in the
die. Remove the lubricant and check to see if it will now
chamber. If it does not chamber, relubricate the case and
adjust the die body down in 1/8 turn increments until it
does chamber properly in
your firearm.
BULLET SEATING
The Gold Medal Seater die
features a sliding case guide
with bullet retention, floating
seat plug and Micrometer
adjustable bullet seating
depth. The thimble of the
Gold Medal Seater Die is
adjustable in .001" incre-
ments. There is no provision
to crimp the bullet with the
Gold Medal Seater Die. To
set up the seater die, turn
the thimble counter-clockwise
(Photo 3)