TWO-MOTION BREEGH-MECHANISM
199
breech-screw completely back in the support ; the travel of
the block for extraction is very much reduced, which
enables the breech to be opened in two actions only.
The head of the hand-lever is slotted, and is in one
piece with a double latch ; it is governed in its sliding
action by an inside spring. The lever is, moreover, fitted
with a joint, which, after the unscrewing of the breech-
piece, lodges in a socket which forms part of the breech-
of the heads of the latch holds the lever to the gun
when the breech is elosed, the other head leaves the
vent free only when the breech-block is placed completely
home.
To open the breech-block, the hand-lever is brought
to the right to disengage the breech-screw ; the lever
is then pulled back, thus withdrawing the breech-screw
in its support, and causing the whole of the mechanism
Figs. 660 to 663. Two-Motion Breech-Mechanism, with Percussion Fuse.
screw support. Firing is effected by means of a line that
causes the friction tube to act.
An automatic double-end ed latch on the right band
of the breech-block support, serves to fix this to the gun
when the breech is closed, and also to hold the breech-screw
to the carrying ring during the opening of the breech.
The head of the hand-lever, in conjunction with the
double latch above referred to, constitutes the means
that prevent the accidentai opening of the breech while
affording complété safety against prématuré fire ; one
to turn round on the vertical hinge-bolt. To close the
breech, these movements are repeated inversely.
This breech-closing arrangement is characterised by
great simplicity and by a small number of parts ; it is
therefore easily worked and kept in order.
Two-Motion Breech Mechanism, with Percussion
Firing- (E'igs. 660 to 663).—This type differs from the pre-
ceding one (see Figs. 658 and 659) only as regards the firing
device, which is specially arrangée! for a percussion fuse.
Percussion is effected direct, with repeating action, the