It would be a pretty easy fix, just need to mirror the updated MrCrayFish's Gun Mod that has the update.

I'm not sure how easy of a fix this is, but I am getting the same thing. Aiming Down Sight through a medium or long scope with shaders enabled causes inside the scope to be a blinding white(or yellow if I look at the sky)

Currently using Magnesium, Iris, and BSL for the shaderpack