This is a simple mod that will adjust the setting for 'Short Range' for your deck gun to 1500m rather than the default 1000m. Your deck gun crew will therefore engage any target from 1500m when you order them to 'fire at short range' through the Watch Officer.
This mod is one that I've been using for a while as I find that the standard 1000m is too close to some ships (especially jimbuna's Q-ships!). 1500m seems to be the best balance between accuracy and the ability to get the hell out of Dodge if the ship I'm attacking has too many weapons.
Mod is available at:
http://hosted.filefront.com/WrefordBrown/2342227