How can you get past mission 4 on Commando 2

You can first shoot the Sniper from behind the truck or rock by jumping up and down. Once he is killed, shoot with the pistol at the side of the rear side of the barrel and it will create ripples and it will move towards you. Once you board it, shoot same way on the new rear side and it will move you to the other end. But remember, you have to really careful when you jump on to the other shore as the cave wall above will not help and you will fall in between the gap between barrel and shore.