Well, I haven't figured out how to add items yet (there seems to be linking to a couple files I haven't quite nailed down yet), but I have been able to mod some of the attributes for guns.
First, if you didn't know, the data files are in "Steam/steamapps/common/Shadowrun Returns/ShadowRun_Data/StreamingAssets/ContentPacks/seattle/data". I've mostly been screwing around the in the items folder. If you're going to be doing any editing, I recommend backing up these folders.
Next, you'll need some sort of hex editor. You shouldn't have any problems finding one on the web. I use xvi32, but just about anything will work.
Opening up the file in the hex editor, you should be able to see a bunch of readable strings. I'll be referencing the "pi 2 ares predator.item.bytes" file. In order to change a string, you'll first need to figure out how long the string will be. The two bytes preceding the string (eg. 12 before "Pi 2 Ares Predator") indicates how long the string will be. This is in hex, so if you don't know how to convert it, look it up.
1 - A string id - don't screw with this
2 - An icon file - I don't recommend changing this either.
3 - In-game text name - You can safely change this
4 - In-game text description - You can change this
There's some other string stuff in there that I can make educated guesses about, but I haven't really tested any of it.
To change the clip size and damage of the weapon, look for the following set of characters after the description:
AD 01 00 00
The two bytes preceding this string is the clip size. The four bytes after this string is the damage. Clip size is easily changed; just convert the value you want to hex. Damage is tricky, as its a float value (ie. it has an integer part and a decimal part). Here are some of the values I've seen:
Code:
Hex Value Damage Value
80 41 16
60 41 14
40 41 12
20 41 10
10 41 9
00 41 8
E0 40 7
C0 40 6