It took me around 15 runs at the first stage to hit the required targets, with each run becoming easier as any perk unlocked is permanent adding a feeling of progression to
your little emplacement; turning it from a puny little one man dugout into a rocket - equipped death bunker dealing out thousands of rounds per minute.
The Chassis is similar, but the benefits / drawbacks are more pronounced as it effects
emplacement options and each Chassis has different weapon hard points, some as
little as one on each side and others with the max three on each side.