I don't know who at Starbreeze decided to make this iron sight look the way it does, and it always put me off using it. This mod simply swaps the rail model for the front iron sight and adjusts the ADS view model positions to compensate for the decreased height. Does this technically make no sense and would it be completely impractical in reality due to only having a single sight post? Yes. Do I care? Not particularly.

In case anyone's curious, while playing around with the way this iron sight is set up I think I know why they did it this way, though I'm not super well versed with how the game handles weapon mods so someone can correct me if I'm wrong:

From my understanding, the game requires a position for each attachment. These attachments positions have to be assigned per weapon, so every weapon has an optic attachment point or a body attachment point for example.

As sniper rifles were never meant to have replaceable iron sights, the original designers never created front or rear attachment positions for those weapons. When Starbreeze were adding the CASSIAN, they must've wanted the front and rear sights to attach to each weapon in places that made sense, but they eventually realised that sniper rifles don't have front and rear attachment points.

Instead of taking the reasonable approach of, you know... adding the front/rear attachment points, they instead created a new model. The Rail™. This model has the required attachment points, and they added the front/rear sights to the rail, saving them the effort of manually creating new attachment points for all 11 sniper rifles that this thing is available for.

Thanks Starbreeze!

This also means the true fix for this unholy piece of laziness is to create new attachment points for all the sniper rifles, but swapping the model is a simple workaround - I have no idea how to make new attachment points or what that would even entail. Someone else can take that on, if they want (the front sight uses a_o_f and the rear sight uses a_o_r, as a starting point).