Page 101 - FAT 105 4.17 MOODLE

Figure 22: A rotating barrel short recoil action.

Recently (2004), Beretta introduced bullet has exited the bore and pressure
the PX4 semi-automatic pistol has dropped. The barrel and locking
(Figure 21), which utilizes the rotat- piece will begin to move backward,
ing barrel short recoil action. driving the slide with it. A tab on the
frame will engage the locking piece
› Roller Lock – The roller lock short
and restrain the barrel. As the slide
recoil action should not be confused
with the roller delayed blowback ac-
tion. Unlike the roller delayed blow-
back action, the roller lock action
uses a locking breech design. The
barrel of the roller lock design also
moves inline.

The roller lock short recoil action
relies on a barrel, slide, locking piece,
a tab on the frame, and rollers. The
slide has recesses cut inside the rails
that correspond with the rollers. The
locking piece acts like a wedge, driv-
ing the rollers into these recesses.

During discharge, the pressure inside
the chamber will cause the locking Figure 23: A Beretta PX4 9mm pistol.
surfaces to hold it closed until the

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