I teach shooting with both eyes open.
Closing or squinting one eye requires more muscles to tighten in the face than both eyes open.
The muscle tightening gets tiresome for extended shooting.
"A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed."
Life Member NRA
Life Member NAHC
Former President of the ECPT (Eifel Combat Pistol Team)