Given his age, his level of experience, the high temperature of the day and the presence of Border Patrol agents where he's shooting, it's doubtful that Sam would risk drinking Jim Beam (bourbon) while hunting. Alcohol dehydrates people, and the very last thing a person wants to be in the desert is dehydrated.
Rifle used, appears to be a sporterized M-1 Garand, with scope mounted too far forward to be useful. Gun is continually cocked after each shot, but this rifle is semi-auto, and reloads itself after ejecting the empty cartridge. It holds eight rounds, but shoots at least a dozen times in a row, and is never reloaded throughout the entire film.
Color of Jim Beam is wrong (too orange), and froths like sweet tea. A guy swilling whiskey from the bottle while driving is unlikely to have alcohol free beer (O'Doul's) in the cup holder. A guy drinking tea from a bottle and near-beer from a can is probably not a hardened killer. More likely an actor trying to stay hydrated and sober.
Sam has a truck, a dog and what appears to be a topographical map of the area where he's hunting. Since he can cover far more area, a great deal faster, than the people who he's hunting, why exactly is he chasing them?
Sam is firing an M1 Garand, chambered in either .30 '06 or .308 (It's a sporterized version). Despite using such a heavy caliber, he demonstrates almost no recoil from his shots. Worse, he makes shots at distances that would likely only hit their target if he was in a prone (laying down) rather than a standing or kneeling position.