HEAT Projectile Stabilization and Accuracy
HEAT warheads become much less effective if they are rapidly spinning, which became a challenge for weapon designers – for a long time, spinning the shell was the most standard method for obtaining good accuracy, as with any rifled gun. However, the centrifugal force of a spinning shell disperses the charge jet. Consequently, most hollow charge projectiles are fin-stabilized and not spin-stabilized. The round could be fired from smoothbore barrel, losing some accuracy.
In recent years it has become possible to use shaped charges in spin-stabilised projectiles by imparting an opposite spin on the jet so that the two spins cancel out and result in a non-spinning jet. This is done either using fluted copper liners, which have raised ridges or by manufacturing the liner in such a way that it has a crystalline structure which itself imparts a spin on the jet.
Besides spin-stabilisation, another problem with any barreled weapon (that is, a gun) is that large-diameter shell has worse accuracy than small-diameter shell of the same weight. The lessening of accuracy increases dramatically with range. Paradoxically, this leads to situation when a kinetic armor-piercing projectile is more usable at long ranges than a HEAT projectile, despite the latter having a higher armor penetration. To illustrate this: a stationary Soviet T-62 tank, firing from (smoothbore) cannon at a range of 1000 meters against a target moving 19 km/h, was rated to have a first-round hit probability of 70% when firing a kinetic (APFSDS) projectile. Under the same conditions, it could expect 25% when firing HEAT round. This affects combat on open battlefield with long lines of sight; the same T-62 could expect a 70% first-round hit probability using HEAT rounds on target at 500 meters.
A further problem is that, if the warhead is contained inside the barrel, its diameter becomes overly restricted by the caliber of that barrel. In non-gun applications, when HEAT warhead is delivered with missiles, rockets, bombs, grenades, or spigot mortars, the warhead size is no longer a limiting factor. In these cases HEAT warhead often seems oversized in relation to the round's body. Classic examples of this include the German Panzerfaust and Soviet RPG-7.
Read more about this topic: High Explosive Anti-tank Warhead
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