As already mentioned and explained with photos - every weapon with aperture sight is more difficult to use in the game/cdlc than it is in real life.
When playing I find myself not using ghost ring irons at all, instead I'm firing from the hip when close and using only scoped variants of M14/M16 from the distance, which imo takes away a lot from the 60/70s experience.
Weapons with notch type rear sight are all fine. Of course these ones could also use slight blurring on rear sight to make it realistic but it's much less of a problem than current non-blurred aperture which obstructs the whole view.
Simpliest solution would be making the aperture hole a little bigger to simulate the way it works irl. This is what you can see in default Arma MX rifles - rear peep sight is of gigantic size. Such big sight wouldn't work irl but because in the game we have only one eye and this virtual eye focuses on all distances at once (unlike reality where your sight can focus only at one given distance and you have 2 eyes) this is a simple and working way to fix the problem.
Best solution would be not only making aperture slightly bigger but also blurring of both ring and everything around it (such as protective wings on M16 carrying handle), or at least blurrying the aperture ring. That way it would look close to how it looks like irl to aim through these sights.
Most difficult to aim are:
Better than above but still hard to use: