Page 119 - FAT 105 4.17 MOODLE

feed sprocket. The feed sprocket features special • The chain will continue through its loop.
T-shaped protrusions that are used to grab and The shoe has once again moved to the
move the cartridges and empty cases. The cycle side of the receiver and is moving back-
of operations for a chain operation action with ward again. The shoe will contact the
an empty breech is as follows: bolt carrier and drive it rearward, extract-
ing the empty case from the chamber.
• The bolt is closed and the breech is
As the shoe continues rearward, the feed
locked. As the motor begins to drive the
sprocket will rotate, moving the empty
sprocket and chain, the shoe on the chain
case out of the receiver (ejecting) and
will move backward (toward the rear
bringing a fresh round in line for feeding.
of the receiver) and will grab the bolt/
carrier assembly and drive it backward.
The loop will continue until the trigger is re-
Simultaneously, the feed sprocket will
leased or the system runs out of ammunition.
rotate and grab a fresh round from the
The major advantage of the chain design is its
feed source and move it in line with the
capability to control rate of fire. The system is
chamber.
capable of firing any number of rounds from
1 to around 550 rpm. This allows very precise
• As the motor spins, the chain will con-
application of fire, unlike the Gatling design,
tinue through its loop, driving the shoe
which is fixed in its rate of fire.
with it. The shoe will continue to travel
through its loops, moving around the The chain design is fairly new compared to
rear of the receiver until reaching the op- other actions and has not seen any use with ci-
posite side as the shoe is moving forward vilian firearms. The chain design has only been
(toward the front of the receiver). employed with military weapons including the
M242 25mm auto cannon. The design was
• The chain/shoe continues forward,
later scaled down to a vehicle-mounted weap-
grabbing the bolt/carrier. The chain/
on chambered in 7.62x51 NATO called the
shoe drives the bolt/carrier into the new
Hughes EX-34.
cartridge and forces it into the chamber.
The advantage to these two types of systems is
As the chain continues forward, the bolt
that because they do not rely on the energy from
head will collapse and rotate in the car-
the discharging cartridge, they are not suscep-
rier, locking the chamber.
tible to the type of malfunctions other systems
• As the chain/shoe reaches its forward- are. With these systems, if a cartridge fails to
most position (before rounding the cor- fire, the external mechanical system will just ex-
ner to pass the front of the receiver), the tract, eject, and load a fresh cartridge. This cre-
shoe activates the cocking piece. ates an extremely reliable action that is capable
of very high rates of fire.
• As the chain/shoe continues around the
front of the receiver, the shoe will contact
the firing tab, which will release the fir- To complete this lesson, take the test.
ing piece and fire the system. Because
the system does not use any energy from
the cartridge, all of the pressure from the
discharging cartridge will leave through
the gun’s muzzle.

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