GWX removes the star shells (SS) and the armor piercing shells (AP) from the SH3 stock game and then sets the high explosive shells (HE) at 250 for both 105 & 88 deck guns.
Go to:
http://www.subsim.com/radioroom/showthread.php?t=186187
and see post #9.
Find the basic file under this path: SH3/data/Cfg/basic. Backup the basic file first, then edit both the 105 & 88 guns to SS=0, HE=200 & AP=40. Or, any amounts you wish; I think GWX made one other change and set the maximum shells to 250. You'll find them way down about an inch from the bottom. Save this edited basic file and you should be all set.
Hope this is helpful.