Armor-piercing, capped, ballistic capped shell

Armour-piercing, capped, ballistic capped (APCBC) is a type of armour-piercing shell configuration introduced in the 1930s to improve the armour-piercing capabilities of both naval and anti-tank guns. The configuration consists of a basic armor-piercing shell, normally an armour-piercing high explosive shell, fitted with an armour-piercing cap for improved armor-piercing properties and a ballistic cap for improved velocity and range.

APCBC diagram
1.ballistic cap
2.armor-piercing cap
3. – shell body
4. – explosive charge
5.driving band
6. – base fuze
7.tracer cup

These features allow APCBC shells to retain higher velocities and to deliver more energy to the target on impact, especially at long range when compared to uncapped shells.

DescriptionEdit

Armour-piercing capEdit

The primary job of the armour-piercing cap (AP cap), also known as just cap, is to protect the tip of the penetrator (the shell) on impact, which could otherwise shatter, decreasing penetration power.[1]

It consist of a metal cap (a metal shell), often solid in structure, which, is mounted on top of the projectile lying against the tip. Depending on the purpose of the cap, different designs exist. Among other things, the cap can be made of soft metal (soft cap), or hard metal (hard cap).[1]

Soft AP capEdit

Soft caps are AP caps made out of soft metal and was the original design in use. Unlike hard caps, soft caps primarily only help with protecting the penetrator on impact.[2] They function by spreading the radial shock outward from the impact along the radius of the now flattened soft cap, keeping the shock from traveling into the body of the shell itself.[2] Soft caps, however, do not function at high impact angles. Starting at obliquities of 15°, they begin to be torn free prior to functioning, and stop fully functioning over obliquities of 20°.[2]

Following World War I, soft caps started being discarded for naval shells. One reason was their inability to function at high impact angles, but also because of improved metallurgy following the war which had led to face-hardened armour that could negate soft cap projectiles.[2] When impacting tough face-hardened armour with a soft cap projectile, the soft cap will protect the penetrator on the initial impact, but due to the properties of face-hardening (hard surface, soft spongy depth), once the penetrator passes through the soft cap and hits the armour, the hardened surface backed up by the soft depth plate will be unable to effectively cave in, which in short leads to the penetrator's destruction by the crushing forces surrounding it.[2]

Hard AP capEdit

Hard caps are AP caps made out of hard metal and were introduced a while after soft caps fell out of favour. Unlike soft caps, hard caps not only helps with protecting the penetrator on impact, but most often also helps guide the projectile into armour at high impact angles.[2] This is achieved by giving the hard cap a blunt shaped tip, often with sharp edges, which allows it to grip into armour even at high impact angles.[1]

Unlike soft caps, hard caps functions against face-hardened armour and even counters it. It does this, much like drilling a hole in wood before one uses a screw, by punching through the hardened surface of face-hardened armour (which isn't possible with a soft cap), destroying itself in the process, which then allows the penetrator to go through the hole in the hardened surface created by the hard cap and penetrate into the soft back of the armour, hopefully going through it or creating spalling on the other side.[2]

Ballistic capEdit

The job of the ballistic cap is to give the projectile a more aerodynamic shape to increase velocity and range, which in turn increases maximum penetration and penetration over range. It consist of a hollow thin-walled metal cone mounted on top of the armour-piercing cap, often by pressing the edges of the cone into a groove circle atop the AP cap. On impact, the ballistic cap will break off or be crushed so as to not impact the performance of the regular cap and penetrator.[1]

DevelopmentEdit

The APCBC munition type was an evolutionary development of the earlier APC (armour-piercing capped) shell design, itself an evolution of the more basic AP (armour-piercing or solid shot) and APHE (armour-piercing high explosive) shell types. With respect to armoured land warfare, the primary intended function of both AP and APHE shell types was to penetrate an enemy armoured vehicle and incapacitate the vehicle and crew by internal explosion (in the case of APHE) or fragmentation/ricochet (in the case of AP rounds).

As the war lengthened, target armour became progressively thicker (and sloped) as new tank designs emerged, and early war AP and APHE became progressively less effective. The initial response to this thickening in armour had been to increase the muzzle velocity in newly developed anti-tank guns. However, it was found that steel shot tended to shatter on impact at velocities upward of about 823 m/s (2700 feet/second).[3]

Based on this deficiency, a new form of shell was developed which was designated APC (armour-piercing capped). In this form of munition, a cap of softer metal was attached to the tip of an AP (solid) round. The purpose of this cap was many-fold. The cap transferred energy from the tip of the shell to the sides of the projectile, thereby helping to reduce shattering. In addition, the cap appeared to improve penetration of sloped armour by deforming, spreading, and “sticking” to the armour on impact and thereby reducing the tendency of the shell to deflect at an angle. However, the cap structure of the APC shell reduced the aerodynamic efficiency of the round with a resultant reduction in accuracy and range'.[3]

Early World War II-era uncapped AP projectiles fired from high-velocity guns were able to penetrate about twice their calibre at close range (100 m). At longer ranges (500–1,000 m), this dropped to 1.5–1.1 calibres due to the poor ballistic shape and higher drag of the smaller-diameter early projectiles. Later in the conflict, APCBC fired at close range (100 m) from large-calibre, high-velocity guns (75–128 mm) were able to penetrate a much greater thickness of armour in relation to their calibre (2.5 times) and also a greater thickness (2–1.75 times) at longer ranges (1,500–2,000 m). Comparative testing of British Ordnance QF 17 pounder APCBC rounds fired into captured German Panther tanks indicated the APCBC munitions were more accurate than late war armour-piercing discarding sabot (APDS) shot.[4]

APCBC shot was produced for a wide range of anti-tank artillery ranging from 2 pounders to the German 88 mm. This type of munition was also designated as APBC (Armour Piercing Ballistic Capped), in reference to the Soviet version of APCBC. APCBC shot was also used in naval armaments in World War II. After World War II, the trend in armour-piercing munitions development centred on sub-calibre projectiles. No tank guns designed since the late 1950s have used full-caliber AP, APC, or APCBC ammunition.[5]

CountermeasuresEdit

One way to defeat APC rounds was to increase the thickness of armour. However, it became increasingly impractical to up-armour vehicles. One alternative was the use of spaced armour, which consists of a thin outer layer of armour sufficient to deform the armour-piercing cap and a main armour layer sufficient to resist the now "decapped" round.

GalleryEdit

NotesEdit

  1. ^ a b c d AMORDLISTA, Preliminär ammunitionsordlista. Sweden: Försvarets materielverk (FMV), huvudavdelningen för armémateriel. 1979. pp. 33, 35.
  2. ^ a b c d e f g http://www.navweaps.com/index_tech/tech-055.htm
  3. ^ a b "Juno Beach Centre – Anti-Tank Projectiles". Junobeach.org. Retrieved 2010-06-12.
  4. ^ U.S. Army Firing Test No. 3, U.S. Army Firing Tests conducted August 1944 by 12th U.S. Army Group at Isigny, France. Report of tests conducted during 20–21 August 1944.
  5. ^ Orgokiewicz, p. 77.

ReferencesEdit