Adding ISA to Fallout: New Vegas
From Nexus Wiki
Requirements: NIFSkope A mesh to edit A mesh to take a pre-existent node from (Vanilla game has these or some modded weapons do) (you can create your own node, but it's just easier to use a node that someone else already made so that's what I will explain)
Adding Iron Sight Animations to any weapons for Fallout: New Vegas is very simple and easy, all you need is the gun mesh you want to add it to. There is one main thing about FNV guns that Fo3 guns don't have, and that is the ##Sighting Node (node) for making it so that weapons will sight properly in the game. And in order to get your weapon to work the same way for FNV you also need this node.
To get this node simply pull up a mesh that already has one, any vanilla game mesh or downloaded mod mesh usually has this. So pull up a mesh that already has one into NIFSkope and right click the node that is labeled ##SightingNode then go to Block> Copy Branch. Go now to the mesh you want to add this node to. Right click on the very first node there, make sure not to click on any of the nodes that branch from it, and select block> Paste Branch. Now you have added the node to your weapon, however it may be mis-named and therefore will not work properly, so now you must right click it and go to Transform> Edit. Once the box pops up you will see a line that you can write in. It may be empty, it may not be, either way, just make sure this box is empty and then write ##SightingNode in it. Keep this box open for the moment you will need it to be sure you get your sighting right. You will notice that there is a view box that shows the actual mesh. Click on the sighting node that you just created and it should highlight for you so you know where it is while you move it. Now come back to that box with the node name in it and look at the numbers in it, these are what you will edit in order to move the node to a different position to add a proper ISA to it. Simply keep editing the numbers until you get the node to be where you want it. Then when you have everything where you want it, click accept, and then go to saveas and save under whatever name you want it to be.
And there it is. You now have a weapon with ISA.