If there is such a thing as an “assault rifle, it’s not the AR-15 that citizens may possess. It would be a fully automatic sub machine gun such as an M-4, M-16, H&K MP5, Uzi or similar weapon. Even soldiers on a battlefield don’t move the selector switch to full auto very often because it wastes ammunition without being as effective as aimed fire. The only time they are really using an “assault rifle” then might be when they are making a sudden assault on an enemy position. Even then, the full auto doesn’t necessarily kill very many of the enemy. The intent is more likely to disorient the enemy making them less effective in returning fire.