102 mm (4-inch) Mark XVI*

These guns appeared on these two ships after their completion in 1941. Jacob van Heemskerck originally had a main armament of 5.9 inch Mark 11 guns, but the needed fire control system couldn't be delivered. This type was very effective against air targets, but too light to be really useful in seabattles.

One of the twin 4-inch mounts aboard HMS Resolution in Gibraltar, 1939

Gun specs
Gun type Mark XVI*
Purpose High Angle/Low Angle (sea- and air targets)
Bore 10,2 cm (4-inch)
Classes used on Jacob van Heemskerck
Isaac Sweers
Date of design 1934
Date in service with RNN 1941 (commissioning of Jacob van Heemskerck)
Length 40 calibers (4,84 m)
Gunweight 2,4 tons
Initial velocity 2651 feet/sec
Rate of fire 20 rounds minute
Shell specs
Shell types HE only
Shell weight 35 lbs
Range (maximum) 12000 meters @ 80 degrees
16200 meters @ 0 degrees
Mount specs
Mount type Mark XIX
Mount armor -
Mount weight 14 tons
Elevation -10 / +80 degrees
Train 340 degrees (+170/-170)
Train method Manual

Twin 4 inch Mark XVI* diagram  (click to enlarge)
A Loading lamp
B Percussion firing lever
C Recuperator cylinder
D Breech mechanism lever
E Breech mechanism lever locking lever
F Safe/fire lever
G Semi-automatic gear link
H Semi-automatic/quickfire changeover lever
I Balance weight
J Recoil cylinder compensating pipe
K Training buffer
L Fuze setting machine, Mark II
M Follow fuze number
N Fuze-setting handle
O Ejector lever
P Safety firing cam
Q Safety firing rolling follower
R Layer's footrest
S Elevation receiver
T Star shell datum spirit lever
U Layer's monocular
V Sighting ports
W Deflection dial
X Range dial
Y Recuperator ram cross-head
Z Cross-head tie rod
a Recoil cylinder compensating tank
b Intensifier
c Interceptor

B.R. 257 - Handbook for the 4 Inch Q.F. Mark XVI* Gun (1941). Link to website and to document.

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