How do i add extra ammo?

Ive been working on modding DEF and script files (Making shotgunish version of bfg[ 3 bfg balls per shot and 99 ammo]), i cant get it working using script files and def files, what am i missing, i stayed up all night and couldn't get it working, please help.

Update: ive worked 2 full days and ive made no progress, im just wanting to get something working, stupid or not to get my feet wet at modding. Ive inspected other weapons mods and they apear to be doing the same thing i am with all the files and such, so ive narrowed it down to the fact that somewere in packing it into a zip file and then onto nameing it a pk4 something goes wrong, could i have some advice on some things i could try?