The factors that regulate
primer selection are:
Powder burnrate is not
constant but accelerates as pressure goes up. The faster pressure
increases, the faster the burnrate will acellerate.
This acelleration in burn rate, ideally, must be kept between certain
levels for most applications. This is the reason why lighter bullets
require 'faster' powder and heavier bullets require 'slower'
Two properties of the
bullet will determine this increase in burn rate. Together these
properties are defined as the shot start pressure:
a). The weight of the
bullet determines how readily it will start moving. The heavier the
bullet is, the higher the pressure needs to be, to get it into
b). The higher the
engraving force of the bullet is when it encounters the rifling, the more
pressure it generates. The engraving force of a jacketed lead core or
monometal grooved bullet is between 3500psi and 9000psi and shot start pressure
is defined as the force required to move the bullet from the seated
position, in the cartridge case, to where the bearing surface of the bullet is
fully engraved by the rifling of the barrel.
GS Custom drive band
bullets are lighter than equivalent length jacketed lead bullets and this slows
the burn rate acelleration of the powder. The engraving force of GSC drive
band bullets are lower and this also slows the burn rate acelleration of the
powder. The engraving force of a GSC drive band bullet is between 650psi
Because GSC drive band
bullets have such a very low engraving force, powder burn rate acelleration is
kept within specification by the use of a magnum type primer that will
ignite the powder more consistently and burn hotter and for longer. Faster
powder is used because of the lower weight for length (specific gravity) of
copper as opposed to jacketed lead.
GS Custom Bullets, situated in Port Elizabeth on the East Coast of South Africa, manufactures solid copper, turned, monolithic bullets for hunting and sport shooting. These bullets
are used by hunters on several continents, hunting from the smallest of antelope to the largest
of dangerous game, using the smooth HP bullet, as well as the more popular HV, FN and SP bullets
with the patented drive band concept. GSC bullets are configured for the highest possible ballistic
coefficients. SP bullets are mainly used for sport shooting. All GS Custom Bullets are coated.