Seems that some entries are missing in the turret's defintion. You may try this:
QUOTE
...
requiredAddons[] = { "CATracked" };
...
class Turrets;
class MainTurret;
class CommanderOptics;
...
class M113MK19: Tank
{
...
class Turrets: Turrets
{
class MainTurret: MainTurret
{
This way, you define most of the turret's elements via the BI's "Tank" class.