The average military recruit could qualify with iron sights with zero background. We only started using optics to help with Positive ID.
Many people don’t practice at all, but an optic doesn’t make up for that.
I am an experienced shooter, so I will allow that my results may not be typical, but it’s not necessary to shoot as much as Form to be proficient. On a black and white target, I can shoot just as precisely (group sizes) and accurately (group location) with an aperture sight as with a scope. But where the scope helps is with accuracy in placing the shot in the right spot on the animal. And in bad light, cover, and all the other adverse conditions in the field.
And, again, limiting lethality in that regard is just plain stupid. We should have a goal - no matter how aspirational it may be - that every animal at which the hunter takes a shot is recovered in a timely manner. If a hunter does not have high confidence in the shot - justified high confidence, not Dunning-Kruger confidence - then he should not be taking a shot.
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“Keep on keepin’ on…”