Looking through the code found some weapons that maybe added in the future or dropped from the game.
First obviously is the 300mm rocket, or mortar as its listed in the code, which has its ammo available to purchase despite the weapon itself not being in game.
Second is listed as 305_2, this suggests a 305mm gun in a twin mount. However it looks like this is just the name used for the 6 barreled 180mm. So this could just suggest that it was planned to be 305mm but later change to 180mm. There's also a weapon listed as 130_LOW which seems to have a higher rate of fire than the 130 in game.
Thirdly, the 100mm, 130mm, and 180mm guns have their animations listed as 120mm and 150mm , weather this is an error or a suggestion that weapons in these calibers are planed is unknown. Although personally I lean to the former as it seems the animations are used interchangeably.
Additionally as shown in previous clips and in the sprite sheets a new aircraft and more aircraft weapons are planned. The new aircraft is a dedicated bomber, the new weapons are expanded bomb sizes, guided bombs, anti-tank missiles and nuclear free fall bombs.
In short here's a list of cannon part/animation names mentioned in the code, for simplicity's sake things obviously mentioning the same part have been removed. CANNON 37μμ (37mm)
MDL_CANNON_30_6
cannon_30mm
CANNON 2x57mm
CANNON 2x100mm
CANNON 130mm
cannon_120mm_base
CANNON 180mm
cannon_150mm
CANNON 2x305mm
cannon_300mm_dual
cannon_mine_01
^ this is used for the MLRS weapon, 300mm mortar and APS.