I agree with Jeff, lifelong alcoholics handle being intoxicated a lot better than those who only drink a bit.
As an example; while a young rookie I once brought a man into the intoxilyzer because of a mistake he made in driving. I could smell alcohol on his breath and person, yet he passed all the tests with flying colors. He walked straight, talked straight and didn't look drunk. But the driving mistake was a red flag and I brought him into the intoxilyzer operator anyway. The operator, the Lieutenant and several other officers said the man was not drunk and I was fairly sure I'd be giving him a ride back to his car.
Within 15 minutes they had an ambulance en-route to the jail. It turned out that the man had such a high alcohol count that he was in immediate danger and needed to be hospitalized. (Yes, you can die from drinking too much.)
It turned out that the man was a lifelong alcoholic and walked and talked better when he was drunk than when he was sober. The intoxilyzer operator stated that he'd seen a lot of people like that; people who drank so much that they coped well with high levels of alcohol in their system.
Based on what I learned from that incident, I would think that if your man wasn't completely over the edge, he'd be well able to complete a sniper ambush if it was something he originally had the ability to do.
Linda