Brief mention has already been made in Tactical and Technical Trends (No. 7, p. 3) of
the German 4.2-cm Pak 41 (42-mm antitank gun). This is a
tapered-bore weapon, being 42 mm at the breech and 28 mm at the muzzle. High
explosive and armor-piercing ammunition is provided. Both the HE and AP
ammunition (see accompanying sketch) are characterized by a relatively large
propellant charge and a flaring skirt or fin at the base of the projectile. The
brass-coated steel shell case is 400 mm (15.75 inches) in length. The skirt of
the projectile, which is squeezed down as the projectile travels through the
tapered bore, serves to give a large effective base area at the commencement
of shot travel. A high muzzle velocity is thus possible with a relatively light
weapon. However, owing to the relatively light weight of the projectile, the
velocity tends to fall off rapidly, and maximum armor-piercing performance is
achieved at short ranges only. The thickness of armor penetration is considerable
in relation to the weight of the gun; the hole made, is, of course, small. Barrel
wear is high; just what the life of the barrel may be is not known. However, in
the case of a similar German weapon, the 2.8-cm Pak 41 (antitank gun
tapering from 28 mm at the chamber to 20 mm at the muzzle) the life of the
barrel is thought to be not over 400 rounds. The muzzle velocity of the 42-mm is
not known; that of the 28-mm is thought to be 4,700 feet per second.
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As indicated in the sketch the HE and AP projectiles are similar in
shape. They are sometimes referred to as arrowhead ammunition. The perforations
or holes (see sketch) are designed to decrease the mass of the skirt
or fin as it is squeezed down into the recess in the projectile casing while
traveling through the bore. The explosive filling of the HE projectile is blue
in color, which suggests Hexagen (trimethylene trinitramine). The nose
percussion fuze of the HE shell is aluminum, with the body in two sections. This
fuze is of the bore-safe type; before firing, the single coil spring keeps the two
half-collars squeezed against the firing pin which is thereby prevented from
being depressed; in flight the centrifugal force created by the rotation of the
projectile forces the two half-collars apart, and the firing pin is then free to move
toward the cap on impact.
The stenciled lettering on the shell case (see sketch) has the following
significance:
First line ............. light antitank gun 41
Second line ............ weight of propellant in grams
Remaining lines ........ data on propelling charge
The HE shell case contains 310 grams of propellant and is so stenciled.