Page 77 - FAT 105 4.17 MOODLE

The charging handle/slide is pulled Of all of the semi-automatic/automatic actions,
to the rear of the firearm, opening the
chamber and breech and cocking the
hammer/striker. At the same time, a
fresh cartridge has been automatically
fed, in-line with the bolt/slide. (2)
• The action spring will drive the bolt/
slide forward, stripping a round from the
magazine and driving it into the chamber.
The moment the barrel and bolt/slide
meet, the chamber is “locked.” (3)
• The trigger is pressed, releasing the
hammer/striker and discharging the
round. (4)
• The energy from the cartridge is
transferred to the bolt/slide, which
overpowers the action spring and drives
it rearward. As the bolt begins to move
back, the extractor begins to pull the
empty case from the chamber. (5)
• The cartridge’s energy will continue to
drive the bolt/slide rearward. Depending
on the model, the ejector may be part
of the bolt or part of the frame/receiver.
When the bolt/slide has reached
the end of its stroke, the ejector will
kick the empty case from the breech.
Simultaneously, the bolt/slide will cock
the hammer/striker. A new round will be
fed in-line with the bolt/slide. (6)
• Again, the action spring will drive the
bolt/slide forward, stripping a round
from the magazine and driving it into the
chamber. The moment the barrel and bolt/
slide meet, the chamber is “locked.” (7)
• If the trigger is still being pressed, it
must be released to the reset position in
order to fire the next round. If the trigger
was already reset, it can be pressed again
to fire the next round. (8)
the blowback action is the simplest. Unlike other
action types, the blowback action does employ a
true locking breech system. The blowback ac-
tion relies on the weight of the bolt/slide and
the strength of the recoil/action spring to hold
the breech closed during discharge. The action
may also employ other methods to help delay
the opening of the chamber.
The blowback action utilizes the momentum
in the bolt from the cartridge being discharged.
When the round is fired, pressure will build in
the case and cause it to expand and seal itself
against the chamber walls. The case will also be-
gin to push against the bolt/slide face. The bul-
let will be pushed into the bore while the case
begins to push rearward against the bolt/slide.
Once the bullet has exited the muzzle and pres-
sure begins to drop in the bore and chamber, the
case will begin to contract and the inertia in the
bold/slide will be great enough to overcome the
recoil/action spring and drive it rearward.
Because the chamber of the blowback action is
not physically locked, the action is typically re-
served for rimfire and low power pistol rounds.
Higher power cartridges require extra closing
force or the movement of the bolt to be slowed.
There are two basic types of blowback actions:
straight or simple and delayed.
• Straight/Simple Blowback – Of the
blowback systems, straight blowback is as
simple as it gets. The straight blowback
system utilizes a barrel and bolt/slide
that simply butt up against each other
to close the chamber. When the action
cycles, the bolt/slide moves straight, in-
line with the barrel. Only the weight of
the bolt/slide and the strength of the ac-
tion/recoil spring are used to secure the
chamber during discharge.
Because the chamber does not me-
chanically lock and the case begins
pushing against the bolt/slide from the
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