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Seating Dies
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While this article is a bit out of sync as the
actual reloading process goes, as we have
not yet discussed priming or metering
and weighing powder, I hope you will allow this
piece to move to the fi nal die/dies needed to
complete the cartridge, the seating and crimping
die or dies.
I believe this makes more sense as we will
complete what you – as a reseller – fi nds in the die
set that is to be sold.
Th e primary function of a seating die is to seat
the bullet squarely, concentrically and to a desired
depth in a highly precise and repeatable manner.
In some cases it may also contain a crimp function
as well.
It consists of a die body, a lock ring, a seat
plug and a small lock ring for the seat plug.
Th is is generally accomplished with a die body
of 7/8” x 14 TPI which has an internal cavity
approximating the shape of the cartridge case but
somewhat larger in its dimensions for free entry of
the case with bullet resting in the case neck. Th e
die body tapers in the neck area to align the case
on center as the bullet enters the seat plug.
Th e seat plug threads into the top of the die
body and controls seating depth of the bullet by
contacting it on the ogive below the bullet tip
or meplat. It stops the bullet’s travel so the case
may be pushed onto it by the action of the ram.
It has an internal cavity to protect the meplat or
bullet point from deformation. Th is also helps to
concentrically center the bullet in the case mouth
during the application of seating pressure as the
press’s ram moves upward causing the bullet to
actually seat. Th e seat plug also has a lock ring to
guarantee the precise depth position for repeatable
seating depth of the bullet. Th ese basic points
apply to both seat dies for bottleneck case and
straight wall cases with some specifi cs to each.
WE DIVIDE THE DIES INTO TWO SUB-TYPES:
A BOTTLENECKED CASE AND A STRAIGHT WALL
CASE.
As rifl e bullets in bottleneck cartridges tend to
be longer and smaller diameter the seat plugs for
them are made in a manner to accept that style
of bullet. Th e internal angle of contact will be
designed for most available bullets but not every
bullet will be best served by the standard seat plug.
In some cases, an accessory VLD type seat plug
will be off ered for use with that type of bullet. It
Redding
Reloading’s
executive vice
president Robin
Sharpless talks
seating dies
in the next
installment of
his series.
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