Editing Armour-piercing ammunition (section)

=== APCNR/APSV ===
{{Main|Squeeze bore}}
{{further|Littlejohn adaptor|2.8 cm sPzB 41|7.5 cm Pak 41}}
[[File:APBCT (cropped).jpg|thumb|German Armour-Piercing, Composite Non-Rigid projectile]]

''Armour-piercing, composite non-rigid'' (''APCNR'') in British [[nomenclature]],{{efn|In case of the british [[Littlejohn adaptor]], ammunition was designated as ''armour-piercing, super-velocity'' (''APSV'').}} alternatively called "flange projectile" ({{langx|sv|flänsprojektil}}) or less commonly "armour-piercing super-velocity", is a [[sub-calibre]] projectile used in [[squeeze bore]] weapons (also known as "tapered bore" weapons) – weapons featuring a barrel or barrel extension which taperes towards the muzzle – a system known as the [[Gerlich principle]]. This projectile design is very similar to the APCR-design - featuring a high-density core within a shell of soft iron or another alloy - but with the addition of soft metal [[flange]]s or studs along the outer projectile wall to increase the projectile diameter to a higher caliber. This caliber is the initial full-bore caliber, but the outer shell is deformed as it passes through the taper. Flanges or studs are swaged down in the tapered section so that as it leaves the muzzle the projectile has a smaller overall cross-section.<ref name="books.google.com"/> This gives it better flight characteristics with a higher sectional density, and the projectile retains velocity better at longer ranges than an undeformed shell of the same weight. As with the APCR, the kinetic energy of the round is concentrated at the core of impact. The initial velocity of the round is greatly increased by the decrease of barrel cross-sectional area toward the muzzle, resulting in a commensurate increase in velocity of the expanding propellant gases.

The Germans deployed their initial design as a light anti-tank weapon, ''[[2.8 cm sPzB 41|2.8 cm schwere Panzerbüchse 41]]'', early in [[World War II]], and followed by the [[4.2 cm Pak 41]] and [[7.5 cm Pak 41]]. Although HE rounds were also put into service, they weighed only 93&nbsp;grams and had low effectiveness.<ref>{{cite book |last=Shirokorad |first=A. B. (Широкорад А. Б.) |year=2002 |title=The God of War of the Third Reich (Бог войны Третьего рейха) |publisher=M. AST (М.,ООО Издательство АСТ) |isbn=978-5-17-015302-2}}</ref> The German taper was a fixed part of the barrel.

In contrast, the British used the [[Littlejohn adaptor|Littlejohn squeeze-bore adaptor]], which could be attached or removed as necessary. The adaptor extended the usefulness of armoured cars and light tanks, which could not be upgraded with any gun larger than the QF 2 pdr. Although a full range of shells and shot could be used, changing an adaptor during a battle is usually impractical.

The APCNR was superseded by the APDS design which was compatible with non-tapered barrels.