Adaptations to existing tank guns were somewhat more difficult, although all major forces had done so by the end of the war. Since velocity has little effect on the armor-piercing ability of the round, which is defined by explosive power, HEAT rounds were particularly useful in long-range combat where slower terminal velocity was not an issue. The Germans were again the ones to produce the most capable gun-fired HEAT rounds, using a driving band on bearings to allow it to fly unspun from their existing rifled tank guns. The HEAT round was particularly useful to them because it allowed the low-velocity large-bore guns used on their many assault guns to also become useful anti-tank weapons.