Corbin Die Set RBT-2 Instructions Manual

							Rebated Boattail Die Set, RBT-2
The RBT-2 die set consists of
two dies and four punches.
The first die is used to hold
the f lat-based jacket while the
core is first seated. This forms
a boattail-shaped base on the
bullet caused by the lead
pressure pushing the jacket
into the shape of  the die.
The second die accepts this
boattailed jacket with its core
already seated, and forms the
rebate or shoulder on the base. The same external punch is used for both
dies, but each has its own  internal punch. The internal punches are used to
eject the bullet on the down stroke.
The final punch is one which accepts the boattail base in a cavity, and fits into
the point forming die (PF-1) which is part of  your jacketed bullet swage set. It
is NOT used in any other die except the optional lead tip forming die (LT-1).
The lead core is NOT seated into the jacket with the usual flat-base core
seating die and punch. Instead, the lead core is swaged in the CSW-1 core
swage, placed in the jacket, and the assembly is put directly into the first RBT
die. The core is seated in this die, using whatever core seating punch fits
inside the jacket best. The same external core seating punch may be used for
flat base bullets in the CS-1 core seater, if  you have one. A shouldered punch
may be required to keep the jacket from extruding forward, depending on the
softness of  the jacket material. Adjustable shoulder punches are available,
optionally, for various lengths of  jackets. The shoulder just stops the edge of
the jacket from becoming longer as pressure is applied to the base. Some
jackets will extrude and become longer under this pressure, even to the point
of  pulling the jacket apart.
The boattail needs to be formed well enough so that it fits correctly into the
second RBT die. Use sufficient pressure to form a good boattail shape. The
second die should form a  sharp step.  In the point forming operation, the
external punch which supports the RBT base will finish the edge of  the re-
bate. Do not use this punch for anything else, as it will crack if  it is not sup-
ported correctly in the die when pressure is applied. If  the bullet is so long
and heavy that there is pressure before the punch is completely inside the die,
the punch will crack. Use a weight and jacket length that lets you get the
punch inside the die for support.
Same External Punch (CS, EXT.)
Bullet base should fit smoothly into the PF EXT. RBT punch. RBT (Rebated Boattail) bullets have these advantages
 over regular boattails.
(1) Muzzle blast dispersion (causing inaccuracy) is reduced by at least 15%.
The muzzle gas is deflected in a ring with the bullet shooting through the
clear space in the center, as compared to the ball of  fire that focuses in front
of  the standard boattail bullet (caused by the laminar f low of  muzzle gas
around the smooth conventional boattail, focusing like a water hose nozzle in
front of  the barrel).
(2) Barrel life is increased and bullet gas cutting is reduced by the sealing
action of  the rebate. Gas pressure acting normal (90-degrees) to the surface
tends to peel a boattail angle back from the bore. The 90-degree rebate shoul-
der makes the gas press straight forward rather than giving it leverage to
vector the force down and pull the gas seal away.
(3) Punch and die life is greatly increased compared to a standard boattail die
set, because of  the thicker edge sections on the punch and the general design
of  the dies.
RBT bullets have one advantage over f lat base bullets.
(1) The air f low over the rebated boattail base is less turbulent than that of
the f lat base design, so drag is reduced by up to 40% in sub-sonic bullets and
up to 15% in super-sonic bullets. A bullet passing through the speed of  sound
will experience an increase in ballistic coefficient below the speed of  sound,
to a greater degree than a f lat base bullet passing through the same velocity/
time curve. RBT pistol bullets tend to strike higher on target provided recoil
and other effects do not affect the attitude of  exit.
BT-1 Slightly smaller bore, no shoulder in the die.
BT-2 Slightly larger bore, RBT internal punch