Page 158 - FAT 105 4.17 MOODLE

Figure 8: A horizontal magazine.

the rounds inside of the body. As the helical basically a box magazine that is laid down on its
magazine is loaded, the rounds push against the side and feeds from the bottom. The horizontal
follower and drive it around the inside of the magazine’s body is even a six-sided horizontal
body (following the channels/fins) and separa- box with a small area near the bottom front for
tor. As the magazine is loaded, the rounds will feeding. Typically, the magazine will lock onto
continue to push the follower back and around the top of the firearm lengthwise (parallel to the
the separator and at the same time wind the barrel), while the cartridges are arranged per-
spiral spring. Typically, the helical magazine is pendicular to the bore’s axis (horizontally). The
loaded from the top rear of the magazine and rounds are loaded from the rear of the maga-
the rounds move forward as they are loaded. A zine and the rounds move forward as they are
variant of the helical design, the “pan” magazine loaded. A spring and follower push the rounds
utilizes the helical arrangement, but unlike the backward into a specialized “spiral” feed ramp
standard helical magazine that arranges rounds that turns the round 90° in preparation for feed-
that point toward the muzzle of the firearm, the ing. The horizontal magazine can be found in
pan arranges rounds around an axis that is per- capacities from 10 to 50+. The biggest advan-
pendicular to the bore’s axis. The rounds inside tage of the horizontal magazine is the fact that
the pan magazine lie flat and stack vertically as the magazine body lays flush against the top
the magazine is loaded. The advantage of the of the firearm and provides a very streamlined
helical magazine design is its large capacity, of- profile. The biggest drawback would be that the
ten 100+ rounds, depending on caliber. Like the design of the feed ramp adds an extra degree of
drum design, the biggest disadvantages of the complexity to a very simple design. A horizon-
helical design are that they are often quite heavy tal magazine design is employed by the FN P90
and complex. A helical magazine design is used and PS90 semi-automatic bullpup rifle.
by the Calico M960 semi-automatic carbine.
The rotary or spool magazine gets its name
Like the helical magazine, the horizontal maga- from the mechanism that arranges and aligns
zine gets its name from the way the cartridges the cartridges. The rotary magazine relies on a
are arranged, instead of the shape of the body. part called the “rotor” to hold and separate the
The horizontal magazine is actually very similar rounds inside the magazine’s body. The rotor
to the box magazine. The horizontal magazine is is similar to both the sprocket from the drum

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