Page 136 - FAT 105 4.17 MOODLE

As the bullet/projectile is being forced smoothbore barrels feature a “forcing
through the bore, the bullet will engage the
rifling and begin to spin. The spin that is
imparted stabilizes the projectile in flight.
The barrel may also feature an integral
chamber (revolvers utilize a chamber that
is separate from the barrel). The chamber
is shaped like its intended cartridge and
is designed to handle most of the strain.
Part of the chamber’s design will include a
“shoulder” of some type that will space the
cartridge inside the chamber.
Just ahead of the chamber is the “throat.”
The throat is a free space that allows the
bullet to pass from the case and into the
lede then rifling with little resistance. The
throat is designed to prevent pressure
spikes in the chamber from the bullet’s
movement being delayed by the rifling.
Just ahead of the throat is the lede. The
lede is like a ramp at the beginning edge
of the rifling. The lede aligns and guides
the bullet into the rifling.
Barrels that do not feature rifling are
known as smoothbore. Smoothbore bar-
rels do not impart any spin on the pro-
jectile and have no throat or lede. Instead,
Figure 10: Different types of rifling.
132
cone” just ahead of the chamber (revolv-
ers use a similar feature at the mouth of
the barrel, just ahead of the cylinder).
The forcing cone decreases the diameter
of the barrel just ahead of the chamber,
compressing the projectiles and creating a
tighter grouping. Smoothbore barrels are
typically reserved for shotguns and shot-
shells loaded with birdshot and buckshot.
There are many different options for ri-
fling, but the different styles fall under
two basic categories: traditional (Enfield)
and polygonal (Metford). Regardless of
style, all rifling is designed to accomplish
the same task: impart spin on the projec-
tile. Traditional rifling consists of a series
of “lands and grooves,” which are raised
and recessed sections inside the bore. The
lands and grooves feature very sharp 90°
transitions between each other, which
leave very defined grooves in the bearing
surface of the bullet. Canted land rifling
is a modified form of traditional rifling.
Canted land rifling still utilizes some of
the same 90° transitions as traditional
rifling, but the land itself “leans” to one
side. The lands themselves are slightly