Lately I have been trying to shoot with both eyes open, as I know this is better.
Mostly to prevent eye fatigue, in my experience.
With scoped guns, I find this easy and indeed much more relaxed; not squeezing my left eyes shut feels better.

However, with my vintage airguns that do not have a scope, I am struggling.
Both with aperture sight as with standard rear sight.
I focus on the target with my right eye for a second or so, then my left eye seems to "win" the focus contest, and I have to close it at this point in order to see things clearly.

I wondered if there are tricks / training techniques to make it easier to shoot with both eyes open?
I remember seeing competition shooters using something in front of their shooting glasses to prevent the "other" eye from seeing the target as well?

Many thanks