Nightmare1, on 23 August 2014 - 09:21 AM, said:
To be fair, one of the primary components of the damage mechanism of BT AC shells (which are of the high-explosive armor-piercing type) is the explosive warhead carried within the projectile, which does need to arm in order to be effective.
(The other components of the damage mechanism of BT AC shells are the sheer kinetic energy of the shell (KE = 0.5 * mass * velocity^2) and the shell's momentum (p = mass * velocity).)
As we've seen with the similar HEAT (high-explosive anti-tank) shells fired by the Abrams MBT in reality, a HEAP shell can travel a not-insignificant distance from the barrel of the weapon before the warhead arms (60-100 feet (18.29-30.48 meters) for the Abrams' M830A1 HEAT shell); at that point, one of the shell's primary damage mechanisms is non-functional, so the shell should impart reduced damage against anything it strikes before its warhead has a chance to arm.
However, there is the "does this make sense" angle that PGI had considered (as evidenced by the response by David Bradley in ATD 05). A MWO AC/2 shell, at 75 shells per ton & 1000 kg per ton, represents a 13.33 kg shell (which includes the casing, propellant charge, and sabot (if any)); likewise, a MWO AC/5 shell represents a 33.33 kg shell, an AC/10 shell represents a 66.67 kg shell, and a MWO AC/20 shell represents a 142.86 kg shell.
If, say, only 10% of the shell's weight represents the projectile's explosive charge... why does a 1.33 kg charge (AC/2 shell) have a 120-meter arming range (the AC/2's canonical minimum range), while a 14.29 kg charge (AC/20 shell) is armed before the shell leaves the barrel (since the AC/20 has no canonical minimum range)? Why does the 3.33 kg shell of a Standard AC/5 have a 90-meter minimum range, when the same-size charge of a UAC/5 shell would have a minimum range of only 60 meters? Why would a Gauss Rifle have a 60-meter minimum range when its slugs are simply melon-shaped lumps of nickel-ferrous alloy & have no explosive warheads to arm, and when the highest velocity said slugs are ever going to have is at the point when they exit the muzzle of the weapon?
Like David Bradley said, "it depends on how justified [PGI] can be in putting [minimum ranges] into the game without them being silly" and "it’s harder to justify why you can’t accurately fire an Autocannon/2 or Autocannon/5 up close, other than it was a balance to their long range in the tabletop game, so they won’t be affected by any sort of minimum range".