All the rifles and pistols are clearly firing blanks, as can be heard by the weak "popping" sound of each shot. Hollywood would be wise to obtain louder-firing blanks for war movies such as this. Also, most of the guns don't recoil when being fired (real high-power .303 caliber cartridges would cause the rifles "jump" noticeably with each shot).
In the first scene, which shows closeups of the soldiers heading for the beach in their attack boat, it's obvious that they're not in a boat at all. There's no up and down motion and no sound of the boat going through water. A stage prop is clearly being used up until the troops are shown leaving a real boat.
Union flag is upside down outside the house when Tolly and his brother are in uniform being given a send off party.