Page 87 - FAT 105 4.17 MOODLE

discharge, the head will immediately against the barrel, and the head, body,
transfer energy back through the body and crank are all in-line, the chamber
and crank. Bearing surfaces on the is fully closed.
body, the crank and receiver force the
The most notable use of the action
body/crank joint to begin to rise. The
was with the Pedersen rifle. The
breech head will continue rearward
T1E3 is a toggle delayed blowback,
(in a straight line) while the body and
semi-automatic rifle chambered in
crank continue to pivot upward. The
.276 Pedersen. The rifle was almost
energy required to drive the crank
selected as the Army’s newest service
upward is enough to slow the action’s
rifle in the 1930s but was passed over
opening until the bullet has exited
by the M1 Garand because of am-
the muzzle and the pressure inside
munition issues. The designer of the
the bore and case has dropped. The
Pedersen rifle, John Pedersen, also
breech head will continue rearward,
designed the hesitation-lock delayed
extracting the case and ejecting it and
cocking the hammer. At this point, blowback action.
the action has reached the rear of its
› Off-Axis Bolt Travel Delayed – The
stroke and the crank has pivoted over
off-axis bolt travel delayed action dif-
90° from its closed position.
fers from all other blowback actions in
The action/recoil spring will drive the fact that with every other action
type, the bolt/breech head/slide moves
the breech head forward, stripping a
fresh round from the magazine and in-line with the bore, while with the
off-axis delayed action, the bolt moves
feeding and seating it in the chamber.
The body/crank joint will pivot down at an angle to the bore. There are two
different types of this action, depend-
until the body and crank are paral-
lel to the breech head and the bore. ing on whether the bolt’s movement
is above or below the bore’s axis.
Once the breech head bottoms out

Figure 11a: Off-axis bolt travel delayed blowback action.

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