Raises the player's base ammo carry capacity to 9999 for each type.
(I say 'base' because, as you can see in the pic, skills, equips, etc, add onto it.)

You still have to be able to buy/find/afford the ammo!
This can actually be a bit of a pain as the single restock purchase option requires you to be able to spend 3M or something like that to restock on everything all at once.
You can just buy things individually though, so not a huge deal, and it's fun to just not buy any of it and just be able to use everything you manage to find in-game.
(You can also just go to any of the free ammo refill points, like the one just before Orcal in Xion, and replenish once that way.)

Installing
Just extract into `StellarBlade\SB\Content\Paks`. (Either directly, or in a `~mods` folder; it doesn't matter.)
Yeah, that's it.
I recommend backing up your save file just in-case.

Uninstalling
As for removing the mod, I believe your max cap should return to normal, but you will probably have to shoot all your ammo to below that cap before it'll stay there.
I really haven't tested this part. YMMV, beware dragons, etc.

Save Location
`%LOCALAPPDATA%\SB\Saved\SaveGames`

Conflicts
Conflicts with anything that alters the file(s):

• SB\Content\Local\Data\CharacterTable.uasset

I PROBABLY WON'T CHECK THIS OFTEN!
I pay much more attention to Nexus comments and will probably forget to check here.