deflection knob counterclockwise until the index points
In emergency situations, where time is extremely
important, the gunner can quickly determine the mask
to 2,700 on the deflection scale and to 0 on the
clearance for any given target by placing his head near
micrometer scale. Notice that moving the knob
the baseplug and sighting along the top of the barrel.
counterclockwise has moved the sight to the left. A
When the line of sight clears the mask, it is safe to fire.
clockwise movement would move the sight to the right.
Of course, it takes considerable time to sight this way
The gunner should always keep in mind that the
before every fire mission; therefore, at the first
barrel moves in the opposite direction of the sight. In
opportunity, determine the minimum and maximum
addition, the gunner must know in which direction the
clearance by using the sight and then record it.
barrel is pointing after a given deflection change.
Any deflection command that causes the barrel to
SIGHT PICTURE
be moved over 90 degrees either right or left of the
principal direction of fire (PDF) is always given as a
The gunner can only have one of two sight pictures
REAR deflection. (For example: DEFLECTION
when the mortar is fired: either the ALIGNED sight
REAR TWO-SEVEN-HUNDRED.) Notice that a rear
picture or the COMPENSATED sight picture. To use the
aligned sight picture correctly, the gunner must lay the
deflection is directly opposite the equivalent FRONT
vertical line of the sight reticle, so it just touches the left
deflection. Any deflection without the command REAR
side of the visible aiming post (fig. 14-16).
is understood to be FRONT.
To use the compensated sight picture correctly, the
After rotating the sight to the new deflection of
gunner must lay the vertical line of the sight reticle, so
2,700 mils, the gunner sets the new elevation by rotating
the left edge of the far aiming post is placed exactly
the elevation knob until the index on the elevation scale
midway between the left edge of the near aiming post
points between 1,100 and 1,200, and the index of the
and the vertical line of the sight reticle. This corrects for
elevation micrometer is pointed at 50 nils.
displacement of the sight (fig. 14-17).
Laying for Direction
SIGHTING
The gunner is responsible for setting the mortar to
As the deflection placed on the sight is greater than
the correct deflection and elevation. Remember, when
95 mils, it cannot be made by turning the traversing
the gunner lays the mortar, the sight is first set for
crank. Therefore, the gunner assisted by the assistant
deflection then for elevation, while the mortar is first
gunner must lay the barrel in the new direction of fire
laid for elevation then deflection. You can readily
by moving the biped. Whenever the biped is moved in
remember this sequence by keeping in mind the key
this manner, the gunner should always rotate the barrel
word DEED.
to the center of the mechanism to give maximum
1. Place Deflection on sight
flexibility at the new setting. As a rule of thumb, the
biped should always be moved whenever the new
2. Place Elevation on sight
deflections more than 20 mils either side of center. Care
3. Level for Elevation
should be taken in moving the biped to get roughly
4. Level for Deflection
within two turns (20 mils) of the aiming posts to avoid
excessive traversing.
For example, we will use the fire command for an
HE round at a deflection of 2,700 mils, charge two, and
With the barrel in its new position and the vertical
an elevation of 1,150 mils. Assume the mortar is facing
cross hair aligned with the left edge of the aiming posts
the principal direction of fire and the sight is aligned
again, the gunner next levels the barrel for elevation by
with the aiming posts at a deflection of 2,800 mils.
turning the elevating crank until the bubble of the
elevation level is centered. The gunner then turns the
adjusting nut of the cross-leveling assembly until the
Setting the Sight
cross-level bubble is centered. After a final check with
the aiming posts, the mortar is now laid in the new
The gunner first sets the new deflection of 2,700
mils on the sight unit. To do this, the gunner rotates the
direction of fire and is ready for firing.
14-11
