How to Swage Bullets Using The
the lead core again and forms the
rebate shoulder on the boattail.
Internal punch is a loose fit, only
Point Former: forms the ogive
curve on the bullet. Use
the RBT external punch.
RBTO-4-M, -S, or -H Die Set
Type -H dies fit into the ram of the Corbin Mega-Mite press (CSP-2), Corbin
Hydro, Jr., (CSP-2H) press, and the Corbin Hydro-Press (CHP-1). The type M dies fit either the horizontal Silver Press (CSP-3) or the vertical Series II
Press (CSP-1). The type -S dies fit only the Series II Press (CSP-1). The last
letter, -M, -S, or -H, describes the outside diameter, threads, punch lengths,
and which presses the die set will fit. If a tool fits both the -S and the -M
systems and there would be no difference in it for either of them (such as
punch holders or draw dies), then the -M designation is used.
The 4-die set consists of a CORE SWAGE (CSW-1), a BOAT-TAIL PREFORM
(BT-1), a REBATED BOATTAIL FINISHER (BT-2), and a POINT FORM (PF-1)
die, each with one internal and one external punch, except the two rebated
boattail dies share the same external core seating punch.
An EXTERNAL PUNCH is held in the FLOATING PUNCH HOLDER (FPH-1M or FPH-1-H), which comes with the press and screws down into the top
plate of the press. For the -M and -S external punches under 3/8-inch caliber,
a threaded bushing and steel ring are removed from the bottom of the punch
holder, placed over the external punch, and then screwed back into the bottom of the punch holder to secure the punch. The punch holder screws into
the press head, so the punch faces the ram. For -M and -S punches from 3/8inch up, the bushing and ring are part of the punch assembly. For -H external
punches, only a threaded bushing is used, without the steel ring. The external
punch is the TOP punch in these systems.
The die screws into the press ram, with its INTERNAL PUNCH inside the
ram. Some internal punches require the use of spring powered retraction: for
the PF-1-H die, the internal punch is called an EJECTION PIN punch, and it
will have a quarter inch diameter hole through the head portion, through which
a 1/4-inch diameter retraction pin fits. The pin goes below the large spring
around the press ram, and pushes down on the pin, which then pushes the
punch down when the ram is raised, making it easier to insert material into
the die. For the PF-1-M and PF-1-S dies, a notch is machined into the head of
the internal punch, which matches a removable pin with knurled head pushed
into the front (CSP-1) or top (CSP-3) of the press. This is the STOP PIN. It
presses on the tail all punches except for the ejection pin punch, to cause
ejection on the down stroke. Because the PF-1 die would form the bullet around
this pin if the pin were allowed to remain in the die cavity during swaging, the
stop pin must be put into the notch and used to keep the pin retracted from
the cavity during swaging, holding it firmly during the down stroke to cause
ejection of the bullet.
External
Punch
Internal
Punch
CSW-1 Core Swage: adjust lead core
weight and shape.
BT-1 Boattail Preformer: seats the
lead core into the jacket and forms
the start of the boattail section.
Same external punch is used in the
next die...
External
Punches are
held in the
press HEAD
using the
Floating Punch
Holder.
Stop Pin
(CSP-1 or
CSP-3 press)
fits the slot in
the ejection
pin punch
head.
BT-2 Rebated Boattail Finisher: seats
used ONLY
the PF die.
used to eject the bullet.
PF-1
External
Punch, is
to push
the RBT
bullet into
Any other
use may
destroy it.
RBT PF
PF-1
Point
Form
Die
In the -H system, a knock-out or ejection bar goes through a slot in the press
ram, below the spring and also below the retraction pin (if one is required—
not all punches have a hole through the head). The knock-out bar supports
the head of the internal punch while the component is being swaged, and
comes to rest on the press mounting plate on the downward stroke. This stops
the movement of the bar while the ram continues down, making the punch
stop moving while the die goes down with the ram.
Internal
ejection
pin
punch,
PF
The RBT deflects
muzzle gas so it
does not focus in
front of the bullet,
as with the
standard boattail.
Never try to swage a component that will not go into
the die by hand. The swaging operation depends on each
component being slightly smaller than the die bore, and
increases the bullet diameter a little with every step. The
core seating die and point forming die are matched to each
other for a given jacket and core material to within 0.0005
to .0010 inches with the core seater being smaller.
The first die is the CORE SWAGE (CSW-1). It is
used to form a piece of lead to precise diameter, length and
weight. There are three bleed holes through the sides of the
die, and its punches are very close fits to the die bore. They
are the smallest punches in the set and only fit this die properly. Always make sure the punch fits the die by hand before applying pressure to it with the press!
For power presses, set the bottom sensor so the pressure stops (red LED on the sensor goes on) just as the
swaged core is ejected (internal punch even with the top of
the die). Use a knock-out bar that allows the punch to come
just to the die face, if you have more than one height of bar
with your press (CSP-2 hand press uses three different
heights of bars for various punch and die lengths). Make
sure your hand press is in the SHORT STROKE (swaging)
position: the CSP-1 and CSP-2 presses have dual stroke pivot
holes for the ram/toggle linkage and you cannot swage in
the long or reloading stroke (it may break the stop pin to
try).
You can use cut lead wire, or a cast lead core. Apply a
small amount of Corbin Swage Lube to the cores as you
handle them. Set the floating punch holder so the desired
amount of lead is left in the die when the press stops moving up (position of the top sensor controls top of stroke on
hydraulic presses, physical end of ram travel is fixed on hand
press). Always extrude at least 1-2 grains from each core,
or else you will not achieve consistent weight control. But
do not extrude more than about 10 grains, as this only wastes
time and raises the swaging pressure unnecessarily.
After making the desired number of cores, clean them
in hot water to remove the swage lube, then let them dry
and insert them into bullet jackets (if jackets are used).
The BT-1 Boattail Preformer is the second die in
a RBT die set. It will accept the jacket for its caliber easily
but closely, and has no bleed holes. The BT-2 looks similar,
but is marked with the BT-2 designation. The bore size of
the BT-1 is slightly smaller than that of the BT-2. The internal punch for the BT-1 die is a loose fit in the die; it serves
ONLY to push the bullet out, and plays no part in forming
the base.
Select a diameter of external punch that fits the jacket
ID at the point where you want the core to be after seating.
Thicker jackets, and lighter cores in tapered jackets, both
require a larger diameter external punch than thinner jackets or heavier bullets with a tapered commercial jacket. (See
Corbin Handbook for discussion of proper core/jacket/
punch fitting).
The correct core seating pressure is normally in the
300 to 500 PSI range. This can vary with the particular caliber, jacket thickness, and other features of the bullet, so
follow any written instructions provided with the die regard-
ing the suggested pressure. Always start with the pressure
in a low setting on the hydraulic presses (300 to 500 psi)
and increase slowly until the jacket expands to just under
the diameter you get with a swaged pure lead slug in the
die. Any greater pressure than this will only stress the die
and could bend punches or break dies.
Apply a small amount of swaging lube to the outside
of each jacket as you pick it up to insert in the die; the amount
that you get by rolling a drop between finger and thumb is
sufficient in most cases. Lubricant should not be allowed
inside the jacket: that is why the cores were washed clean
before insertion into the jackets.
The third die is the REBATED BOATTAIL FINISHER (BT-2). Note that the combination of the BT-1, BT-2,
and the external RBT punch for the PF-1 die is also packaged
as the RBT-2 ADD-ON SET, for adding the RBT design to
existing flat base die sets. Use the same external punch (core
seating) that you used with the previous step. Push the bullet base first into the die, and apply enough pressure so that
a shoulder is formed clearly at the junction of the boattail
and the bullet shank (full diameter portion). This small shoulder is the "spoiler" that breaks up laminar flow of muzzle
gas so it cannot focus itself in front of the bullet, gaining up
to 15 percent better accuracy than a conventional boattail
with all other factors equal. The shoulder formed in this die
must match the cavity of the external point form punch. If it
is too long or short, a double shoulder may be created in
the final step.
The fourth die is the POINT FORMER (PF-1-H).
It shapes the ogive curve on the bullet and gives the bullet
its final diameter. This die has a bullet-shaped hole. The
diameter of the point form die itself is usually NOT the same
as the bullet, and is designed to match the core seater, the
jacket material and thickness, and the lead hardness. Using
materials other than those for which the set was designed
can change the bullet diameter and may cause the bullet to
stick or become hard to eject.
The external punch has a cavity matching the boattail
angle and shoulder depth. Make sure that the bullet is short
enough so that the entire punch tip is well within the die
cavity before any pressure is created. If the punch walls are
not supported fully by the die, the punch will crack when
pressure is applied. Making too heavy a bullet for the length
of the PF-1 die cavity may break the external punch.
When installing the internal punch, make absolutely
sure that the internal ejection pin punch is held by the stop
pin (in -M or -S systmes) or retraction pin (in -H systems).
Otherwise the pin may fall out of the die hole and be collapsed by the end of the die when the ram goes down, rolling it like a pretzel inside the ram. Shape the bullet by carefully raising the ram and pushing the nose end of the bullet
down into the die.
Eject, examine, and re-adjust until the tip is formed to
the desired amount of closure, but do not try to close it
smaller than the size of the ejection pin! Never force jacket
material up into the ejection pin hole: doing so will concentrate force in such a small area that it can crack the die.
Remember, we are dealing with rifle chamber pressures in
these swaging dies, when the press goes "over center".
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