Open items.xml with notepad(++), press ctrl + h (replace function), replace the words "Normal", "Uncapped" and "Capped" with "UnlimitedOnResearch". Then search for ammo.alien, and turn the first one to Capped again, because this is the original alien ammo which will crash the game if you open the energy tab with it enabled.
UnlimitedOnResearch does not work for every time though and this might be not what you want.
I personally allways get rid of the ammo manufacturing by opening itemx.xml with MS Excel, just simply copying "Unlimited" from basic armor and pasting it onto every line starting with "ammo.".
If you only want the starting equipment of be unlimited, I could post a modifed script which makes you start out with more weapony in the storage, but not change anything else.