Programming noob in need.

[krzys_h]

The range of the tower is more or less the same as shooter's range (40)

It's actually 200 engine units, which is 50 meters in-game if I'm reading the code correctly.

Shooters fire range is 0.8 seconds at speed of about 200 engine units/second, which is equal to 50 meters a second, which in turn gives the well-known value of 0.8*50=40 meters.
There is also a small speed randomization which makes the particles look more natural because they don't go in a straight line, but may interfere with this result a bit.

All these calculations assume the default value of g_unit=4 (the game unit to engine unit ratio)