Measurement of Heat Input into the 105mm M68 Tank Cannon Firing Rounds Equipped with Wear-Reducing Additives.
ARMY BALLISTIC RESEARCH LAB ABERDEEN PROVING GROUND MD
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Four in-wall thermocouples were used to measure the total heat input to an M68 tank cannon at 641.4mm from the rear face of the tube. This is the distance where vertical land diameter is measured to judge remaining tube life. Heat inputs were measured for 105 mm ammunition with known life in order to assess probable wear life for a developmental 105mm projectile that is lighter than the M392A2 APDS round. In addition, attempts were made to modify the liner in the M456A1 and M490 TP-T rounds to try to reduce the erosiveness of these projectiles. It was found that replacing the existing 24.1cm-long TiO2wax liner with liner with a 30.5cm-long talcwax liner significantly reduced heat input to the barrel. It was extimated that the use of the talcwax liner on the lightweight 105mm round would put the wear life in excess of the fatigue life. Serial firings of the rounds with TiO2wax additive showed that at least ten rounds had to be fired before the heat input reached a stable value. This heat input was much lower for the M39242 APDS round with a folded TiO2wax liner than it was for the M456A1 HEAT round. This is consistent with the ten-fold higher wear life for the APDS round of 10,000 rounds.