The forward movement of the mechanism (described in detail below) provides the following :—
(a) The succeeding round is positioned into the T cut of the bolt and is fed into the chamber.
(b) The ejector ejects the spent case.
(c) The bolt closes and the breech is locked.
(d) The trigger bar engages the sear slot ready to release striker on trigger being pulled.
(e) The next cartridge in belt is fed into position in the feedway, and is gripped by the extractor, ready to be withdrawn from belt on the next rearward movement of the mechanism.
bolt accelerator barrel extension barrel
The compressed driving spring reasserts itself, driving the bolt forward. The succeeding round is positioned by the extractor into the T cut of the boh head and is carried forward into chamber.
The bottom projections of the bolt strike the tips of the accelerator claws, tipping them forward and unlocking the barrel plunger ; the barrel plunger spring reasserts itself, driving forward the barrel extension and barrel. The breech lock rides up the breech lock cam to lock bolt to barrel extension and barrel. The sear notches engage the trigger bar. The tip of the cocking lever is returned to its fully backward position. (It should be noted that, should the mechanism not go fully forward home, the cocking lever will not be right back, thus preventing the striker from striking the cap of the cartridge.)
belt feed feed lever feed pawl cartridge stops
The feed lever actuating stud riding in its cam groove in the bolt is driven to the left, thus its forward end carries the feed slide to the right, carrying with it the belt feed pawl, belt, and succeeding round until the latter abutts the front and back cartridge stops in the feedway. The succeeding round is now in position for the extractor to extract it.
During the first part of the bolt's travel forward the extractor feed cam, situated on the left plate of receiver, strikes the extractor plunger and guides the extractor downwards, finally positioning the base of the succeeding round in T cut of bolt, and nose of bullet into chamber.
The ejector (at the bottom of the extractor) strikes the spent case (if it has not already fallen out), which has been withdrawn from the chamber (the rim of spent case being in T cut of bolt head), and ejects the spent case through the ejector'port opening in the base of the receiver.
When the bolt has nearly closed, the extractor is forced up by a steeply inclined cam on the left plate of receiver, thus releasing its grip of the cartridge, which has been fed well into the chamber. The extractor rides upwards and over the base of the next cartridge in the belt in the feedway. The extractor spring in the cover forces the extractor down and on to this cartridge, thus gripping it securely ready to withdraw it on the next rearward movement of the mechanism.
55 Front legs,
56 Front leg jamming handles.
Tripod Mounting, Model 1918
57 Trail leg jamming handles.
58 Trail leg.
the tripod mounting (model 1918)
The illustration above dearly shows the various parts.
To mount gun, turn elevating and trunnion pin handles to vertical position and withdraw. Place gun on tripod so that its mounting holes coincide with the trunnion bracket holes and elevating bracket holes. Push in trunnion pin, and turn trunnion pin to lock; reinsert elevating pin and turn to lock.
Loosen pintle lock handle, and adjust traversing dial to a horizontal position. Tighten pintle lock handle, making certain the teeth on the locking plunger are in firm engagement with the toothed sector. Place ammunition box in bracket situated on left side of tripod.
59 Front leg dutch plates.
60 Pintle locking handle.
61 Traversing mcchanlsm clamp.
62 Slow-motion traversing wheel.
63 Slow-motion traversing dial.
64 Slow-motion traversing dial zero adjustment lock nut.
65 Traversing dial, 65a Pintle.
Tripod Head, Model 1918
66 Elevating clamp.
67 Slow-motion elevating hand wheel.
68 Slow-motion elevation dial.
69 Slow-motion elevation dial pointer.
70 Elevating pin,
71 Trunnion pin.
72 Ammunition box bracket.
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