I heard somewhere that the sleeping drug temazepam improves marksmanship by steadying your aim. Is this true? How does it work? How much of the drug should I take in order to improve my marksmanship and not fall asleep? Please give me as much information as you know that relates temazepam to better marksmanship.

Do not take drugs to learn to shoot better, shooting better is a matter of proper holding of the weapon and breath control.
Do it right or don't do it at all