Armor-piercing, capped, ballistic capped shell
Armour-piercing, capped, ballistic capped (APCBC) is a type of configuration for armour-piercing ammunition introduced in the 1930s to improve the armour-piercing capabilities of both naval and anti-tank guns. The configuration consists of an armour-piercing shell fitted with a stubby "armour-piercing cap" (AP cap) for improved penetration properties against surface hardened armour, especially at high impact angles, and an aerodynamic "ballistic cap" on top of the AP cap to correct for the lower aerodynamics otherwise created by the stubby AP cap, which would lower velocity and hence range. 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. The configuration is used on both inert and explosive armour-piercing shell types: The APCBC configuration is an evolution of the earlier APC configuration (armour-piercing, capped), itself an evolution of the simple AP configuration (armour-piercing, uncapped). The APCBC configuration is however expensive and thus a large amount of both historical and modern armour-piercing ammunition uses only one of the two caps: APC (armour-piercing, capped) & APBC (armour-piercing, ballistic capped ). Design. Ballistic cap. The "ballistic cap" ("BC") is a hollow thin-walled aerodynamically shaped metal cone mounted on the top of a projectile to cover it with a more aerodynamically efficient shape. This reduces drag in flight, so higher velocity and hence range is obtained giving better penetration over longer distances. On impact, the ballistic cap will breaks off or collapse without affecting the impact performance of the armour-piercing cap and penetrator. Ballistic caps are used on a great variety of projectiles other than APCBC shells and exist to allow the projectile or cap underneath to have a less  aerodnyamic shape more suitable for the effect of the munition. They are most often fitted by pressing the edges of the cone into a groove around the edge of the projectile or AP cap. Armour-piercing cap. The primary job of the "armour-piercing cap" ("AP cap", most often shortened to just "cap") is to protect the tip of the penetrator (the shell) on impact, which could otherwise shatter and not penetrate. It consist of a metal cap, 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'). History. Early World War II-era uncapped AP projectiles fired from high-velocity guns were able to penetrate about twice their calibre at close range: . 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. As the war progressed, vehicle armour became progressively thicker (and sloped) and early war AP and APHE was less effective against newer tanks. The initial response was to  compensate by increased muzzle velocity in newly developed anti-tank guns. However, it was found that steel shot tended to shatter on impact at velocities greater than about 823 m/s (2700 feet/second). To counter this a cap of softer metal was attached to the tip of an AP (solid) round. 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. Later in the conflict, APCBC fired at close range 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 17-pounder (76 mm) gun and US Army APCBC rounds fired into captured German Panther tanks indicated the APCBC munitions  were more accurate than late war armour-piercing discarding sabot (APDS) shot, though the lot used was described as sub-standard and the report made no determination of general APDS accuracy. 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.