Changelog

1.2.0:

-Got mod working with 0.13.
-Had to copy the old explosion file as it no longer existed in factorio base.
-Minimum range has now been implemented!!!! This is huge. No longer will the turret destroy its own defences.

1.0.1:

-Changed item location in crafting grid. Now the artillery is with the gun turrets.
-Fixed wrong explosion in use for shell impact. Should have been Huge-Explosion, was only explosion.
-New muzzle flash animation. 
-I intended the cost of the cannon and shells to offset the power of the damage, the feedback that it was cheap to construct and maintain lead to the following changes:

Research increased from 60 X (2 red, 2 green, 1 blue).
to 90 X (1 red, 2 green, 3 blue).

Price of cannon increased from 50 Steel, 5 motors, 2 radars, 1 processing unit.
to 100 Steel, 25 engines, 2 radars, 10 processing units.

Price of shells increased from 3 for 5 steel, 5 explosive.
to 1 for 12 steel, 6 explosive.

Hopefully that is more in line with "expensive", however due to peoples bases being different this may not be the case or might be overboard and putting it out of reach of some players. Let me know, feedback appreciated.