I know this topic is over 4 years old, but it's the first thing I came across when trying to figure out how to edit the attachments on signature weapons myself...and since there's no replies, I thought I might as well post my findings so no one else has to scour the 267 page "Mods for Far Cry 3" thread on the Ubi forums trying to figure it out.
This assumes you already know how to access and edit the WeaponProperties XML files. If you don't, here's a tutorial for that.
1. Open up the XML file for the signature weapon you want to edit (e.g. KSV.Shredder.xml for the Shredder)
2. Find the attachment you want to edit by doing a search for "text_attachmentAttachmentType" the name of the attachment should be in this field (e.g. silencersmg, optical, etc.)
3. Look a couple lines down from that to find the following field: <field name="bAttachAtStart" type="Boolean">False/True</field>
4. To add an attachment, set <field name="bAttachAtStart" type="Boolean">False</field> to True
5. To remove an attachment, set <field name="bAttachAtStart" type="Boolean">True</field> to False
6. Make sure you don't have 2 conflicting attachments enabled at the same time. For example, a reflex sight and an optical sight.
7. Then just save the XML, repack everything, and you're good to go.
Say you wanted to replace the Optical Sight on the Shredder with a Red Dot...you'd do a search in KSV.Shredder.xml for "optical" and change the "bAttachAtStart" field in that section to False, then you'd do a search for "reflexa" and change that "bAttachAtStart" field to True
For most signature weapons this is all you should have to do. It's worth noting, though, if you currently have one of the signature weapons you edited equipped when you load a save, you'll have to unequip and then re-equip it before you'll see the changes.
However, adding a silencer to the AMR is slightly more complicated, because you also have to remove the muzzle break (which is one of two attachments named "none" in the XML file.)
Here's a step by step tutorial on how to do it:
1. Open M93.AMR.xml
2. Search for: <field name="text_attachmentAttachmentType" type="String">silencersniper</field>
3. Look a few lines down from that and change: <field name="bAttachAtStart" type="Boolean">False</field> to True
4. Now you need to find and remove the muzzle break, it should be in the very next <object name="Attachments"> section after "silencersniper". There's 2 attachments named "none" but the muzzle break will be the first one. It will also be the only "none" attachment with an ID other than 0 in the "arkAttachmentArchetypeName" field. For me, the ID was "7703373589865"
5. In that attachment section, locate: <field name="bAttachAtStart" type="Boolean">True</field> and set it to False
6. Save and repack.
Hope this helps, and good luck!
EDIT: I've also figured out how to add explosive rounds to the regular Z93:
1. Open up M93.AMR.xml and do a search for "explosion" which should bring you to <field name="selStimType" type="Enum">Explosion</field>
2. You'll need to copy this entire "Stim" section. It starts one line up, from <object name="Stim"> to just before the next <object name="Stim"> (36 lines in total).
3. Open up M93.xml and search for "ImpactStims" which will bring you to the field <object name="ImpactStims">
4. Go to the end of the ImpactStims section, the line after </object>, and paste in the section you copied from M93.AMR.xml
5. Save and repack.
These instructions seem a little confusing, but if you're familiar with editing the XML files it should be pretty straightforward. Basically, the explosive rounds are tied to a "Stim" object present in M93.AMR.xml, but not in M93.xml, so if you compare the two you should be able to spot the section that needs to be copied fairly easily.
Edited by metaphoria, 05 November 2017 - 11:55 AM.