USSR has pioneered the use of APFSDS ammunition with the introduction of T-62 medium tank. With their extremely high speed and long direct-fire range these rounds could be effectively used at substantial range in spite of the antiquated fire control of T-62. Opposite to the popular belief, it was not however a prefered anti-tank round until end of 70s, with HEAT being considered more versatile, accurate, and powerful.
The principal difference of Soviet APFSDS rounds from the Western ones is that the former use bore-riding fins and the sabot has only one point of contact with the barrel, while the latter use spool shaped sabots that touch the barrel in two points and therefore can afford to have subcaliber fins. At first glance there are advantages and disadvantages to both approaches. In Soviet model, the sabot can be made much lighter and therefore the loss of gunpowder energy on acceleration of parasitic mass is smaller. On the other hand, large bore-riding fins produce a high ballistic drag causing severe decceleration of the projectile in flight and affecting stability. The developments of the last decades have shown that the Western approach seems to be more sound. Newest 125mm rounds have moved away from bore-riding fins, and there are many foreign variants of 125mm APFSDS rounds utilizing spool-shaped sabots.
Soviet 125mm APFSDS rounds have the following layout (the round assembly depicted is 3BM-16/3BM-18): in the front of the projectile is a ballistic cap (1) which covers the flat nose of a penetrator body (2); there is a ring-shaped three-part discarding sabot (3) with a driving band (4); stability in flight is provided by means of 5 bore-riding fins (6), that are equipped with ballbearings (7) for centering in the barrel. The round is assembled with the incremental charge (5).
In addition to the incremental charge integral to the round, the standard propelling charge (4Zh40 or 4Zh52) is used; APFSDS rounds have an initial velocity between 1700 and 1800 m/s, and velocity loss of 80-150 m/s/km depending on the model.
The separated sabot petals possess significant kinetic energy and are considered a safety hazard out to 1000m and 2° to each side of the gun.
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