Just to make sure your doing it right.
Hold L trigger to bring gun up > click right stick to aim down site/ iron sights > (while still holding L trigger) hit right D pad to switch to scope. Holding right d pad takes you back to iron sights. I have use all sights but PSO and N8ght vidon without issue on Mosin, SK, CR, UMP, M4, and SG5.
Bino's, range finder, or scopes currently do not work in hand to look at stuff.