July-August - Air Defense Artillery School

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/9-13 THE .50 I\IACHI0JE GU0J AS A SlIBCALIBER "40" 21
mu~tclosely approached the 40mm in muzzle velocity and
racer burn-out point.
In using this subcaliber mount with the Director 1\'15 or
\16. or with forward area sights, single shots are fired nor-
~ally by means of the butterAy trigger mounted on the
achine gun. A satisfactory rate of fire for the earliest
ta~es of training is obtained if the gunner counts to three
a moderate rate between shots. This rate of fire should
increased in proportion to the increase in skill of the
n crew until a combat rate (one shot per second) is
ached.
The employment of this subcaliber weapon is satisfactory
r all targets firing within its tracer burn-out range. Since
his range varies between 1800 and 2000 yards, the lower
these figures should determine the maximum firing limits
the Course.
AD)UsT:\rENTs TO DmECTOH
'I he great virtue of the caliber .50 as a subcaliber weapon
r the 40mm is the minor character of the adjustments necry
for nre with the director, 1\15 or 1\16. The supervation
(9.) of the two guns is so nearly the same for all
ges within the tracer burn-out point of caliber .50 amunition
that no adjusting of the superele\'ation cam fol-
'er in the director is required. The slight difference in
Uzzle velocity makes for only slight differences in the
nect range settings on the director. Differences at the
Figure 2
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close ranges arc small enough to be ignored. At longer
ranges the range seller can discriminate by deliberately
sensing longer ranges or by pasting an adjusted range dial
O\'er the standard dial. The following tabulation forms the
basis for adjustments in the range selling:
Act /fal Hange of Target
600 vards
1,000 "
1,400
2.000
Proper Hallge Settillg 011 Director
Dial For Caliber .50
DESCIUPTION OF ADOPTER
645 vards
1,100
1,600
2,400
In order to make subcaliber fire possible. adopters or
mountings have been devised which fit on the regular
mount. The one described here was developed by 1\ la jor
James Glover, CAe. It has been in use for some time by
several units in training at the AAATC, Camp Davis, N. C.
and has been found entirelv satisfactorv. The construction
of this mount necessitates ~ertain fou~dry work since the
main parts are made of cast steel or grey cast iron. The final
tapping, welding and machining can be done by local ordnance
shops. The attached machinist's drawings 1, 2 and 3
give dimensions and diagrams and no attempt will be made
here to duplicate details of construction. A word or two of
general description. however. may prove helpful. The
mount is made up of two main pans: (I) a hea\'y cast steel