The movie is from the 1980s, American, about a group of friends who went hunting and met another group hunters in the forest. Somehow they became hostile and started shooting at each other. Some got wounded, I am not sure if anyone was killed. They went back home, and started preparing to go again to the same place and this time be ready to fight, and the whole movie is about their preparation. Finally they went back looking for the other group, and found out that they were being preparing even better, they had dug tranches in the ground, masked themselves inside and when our guys came they opened fire and totally annihilated them. Crazy and shocking end.

Sounds like Shoot