Reports of the enemy's defense of Guadalcanal included information
concerning the employment and effectiveness of the Japanese 47-mm antitank
gun (see Tactical and Technical Trends, No. 19, p. 5). Detailed information about
this gun has now become available and it is presented herewith.
|Tactical Use|| ||Antitank and antipersonnel|
|Caliber||47-mm (1.85 in)|
|Manufacturer||Osaka Army Arsenal (1942)|
|Breech mechanism ||Horizontal sliding (semi-automatic) |
|Firing mechanism ||Percussion hammer |
|Recoil mechanism ||Hydro-spring|
|Carriage||Welded steel with pneumatic tires|
|Rifling||16 lands and grooves, RH twist |
|Length of gun||99.48 in|
|Length of rifling||83.30 in |
|Length of chamber||11.10 in |
|Diameter of grooves at muzzle ||1.89 in |
|Diameter of lands at muzzle ||1.85 in |
|Weight of HE projectile||3.37 lbs |
|Weight of AP projectile ||3.08 lbs |
|Average velocity HE||2,735 f/s |
|Average velocity AP ||2,710 f/s|
|Ammunition||HE w/PD fuzes; AP and HE |
|Shield||4-mm steel armor|
Marking (with translations) found on gun
| ||Type 1 (M-1941)|
| ||47-mm. Gun (Anti-Tank)|
| ||No. 21 (Gun Serial No.)|
| ||Made in Showa 17 yr. (1942)|
| ||Osaka Army Arsenal|
Marking (with translations) found on rubber tires
| ||Trade Mark of Yokohama Rubber Co.|
The tube is of built-up construction. It consists of a long barrel with a
heavy reinforcing muzzle band, common to Japanese pieces. The tube is sweated
into a jacket which in turn is attached to the breechring. The breechring is
machined to receive the tube and the breechblock.
The breechblock is of the sliding wedge-type and is semi-automatic. It
opens automatically on counter-recoil by the action of a lug under the left rear
of the breechblock catching on the 'flexible cam as the gun returns to battery. As
the breechblock opens, the empty shell case is extracted. The breechblock is
then held open as the extractor catches in a machined groove of the block. When
another round is rammed into the weapon the rim of the cartridge case trips the
extractor and the release of the tension on a spring enclosed in a cylinder above
the breechring closes the breechblock.
The firing mechanism, of the percussion hammer type, is hinged to the
lower part of the breechring and can be fired either by a lanyard or by pressure
on the firing plunger located in the center of the elevating handwheel on the left
side of the weapon. The firing mechanism is recocked on counter-recoil.
b. Lower Carriage
The trails are of welded steel construction and can be spread to a 60°
angle for firing. At the rear of the trails are flat spades containing vertical
openings for inserting steel plates. These stabilize the piece while firing. When
travelling, the trails are fastened at the rear by a trail lock (loop and hook). The
trails are fastened to the axle assembly by open, hollowed hinge pins. Hinge pin locks,
consisting of plunger and lever, keep the trails in a closed position.
The axle is eccentric in that the ends extend into a shock-absorbing
assembly, held in a cylindrical housing. The eccentric axles are locked to the
housing when firing and disengaged when the weapon is travelling. There is
knee action effect when the weapon is being towed.
The disk wheels are mounted on 8-ply, rubber tires, 3 inches by 5 inches.
The tires are filled with an air-spaced material as there is no valve for inflating
|JAPANESE 47-mm AT GUN|
c. Top Carriage
The top carriage consists of an irregular shaped steel base that pivots
in traverse on the lower carriage. Trunnion seats are found to position the cradle
of the weapon. The traversing and elevating gears are also found on the top carriage.
The U-shaped cradle is attached to the top carriage at the trunnions. The elevating
arc is attached to the rear of the cradle with a pin. The recoil mechanism is
attached to the gun tube by the nut on the buffer cylinder. This cylinder moves
with the tube in recoil and the piston rod remains stationary. The mechanism
is composed of three spaced coil springs and the cylinder contains about four
and one-half pints of glycerine and water.
The elevating mechanism consists of a handwheel and two series of beveled
gears and shafts extending to a worm and worm wheel. This in turn rotates the
pinion which is housed to the rear and is part of the top carriage. The pinion
contacts the elevating arc which is secured to the cradle and elevates the weapon.
Both the elevating and traversing mechanisms are found on the left side of the piece.
d. Sighting Equipment
Sighting equipment on the gun examined is incomplete but the available
parts indicate that a straight tube telescope is used for sighting. The sight
bracket is mounted on the left and the range drum on the right of the piece. The
window for the range drum is wide enough to allow the reading of three scales on
the drum. It is assumed that the range drum has a range scale for the AP-HE
projectile, the HE projectile, and a scale graduated into regular angular divisions.
The telescope holder rides on a cam which is actuated by a shaft leading
from the range drum across the top of the breechring. The cam has a regular
curve but is mounted eccentrically to elevate or depress the sight, through the
angle necessary for super elevation.
The shield is constructed of 4-mm steel armor and is fastened by four
brackets to the top carriage. Openings in the shield allow for sighting. An apron
of the same thickness of steel is attached to the lower carriage of the weapon and
affords protection from small arms and shell fragments.
f. Firing Program
Five rounds of Japanese AP/HE ammunition and five rounds of Japanese
HE ammunition were fired in the gun examined. The gun was star-gauged before
firing. Form factors were estimated for both types of projectiles. Results of
the tests were:
(1) AP/HE Projectile
Powder charge 14.00 oz
Length of recoil 18 3/4 in
(2) HE projectile
Powder charge 14.00 oz
Length of recoil 18 1/2 in
Pressure gauges were placed in one round of each type of ammunition.
All gauges but one were lost and this one, from an AP/HE round, indicated the
pressure to be 20,600 pounds per square inch.
*Generally known as Model 1 (1941) because designed in that year.