"Multiple studies have shown benefits of caffeine in improving endurance. Military studies have shown caffeine increase vigilance in sleep deprived and one study showed improved shot group tightness."

"Recommended dosing is 5mg/kg of bodyweight. Dosing of 200-300 mg has also been used. Higher dosing has been associated with side effects that would decrease performance. Serious adverse reactions have been seen at 2,000mg so this quantity of caffeine should be avoided."

The military does some cool studies on these. Source is below, but you can find the actual study with charts on how firearm proficiency rises and drops with dose.

https://www.benning.army.mil/tenant/75thranger/content/PDF/R...