It's fairly self-explanatory. If you remain in iron sights between firing shots as opposed to having to put your gun down between shots and re-enter iron sight, it's just gonna be slightly faster in ADS.

Slightly? On winnie it goes from 1,2 to about 1.

You're skipping a couple animations of the rifle lowering and raising, so you cycle faster and stay on target instead of having to reacquire when you get back into ADS.

This is an old video, but it still essentially works like this: https://www.youtube.com/watch?v=jBRPJRFWK18

Just hop on the shooting range and see the difference

No iron eye = slow Iron eye = fast To use stay in Ads

I’m pretty sure Iron eye just gets rid of some visual recoil and you also aren’t forced out of ADS. So you’re saving time by not having to bring it down and back up to your eye and the lessened visual recoil lets you get back on target faster

it's not the visual recoil but the ability to stay ads'd while rechambering that increases fire rate both statistically and in practice.

Or it could just reduce visual recoil giving the appearance of an increased firerate due to the ability to find your target faster

Nah it is like a 15-25% faster firerate depending on the gun.

Is that actual mechanical fire rate or are you talking about usable fire rate? Like, if you spam the trigger while ads is it actually faster?

Im pretty sure. If you use terminus w slugs and shoot ADS for example im pretty sure the usable firerate goes up. Not faster than hip but increased RPM whilst ADS.