The only important thing to know is they're loud and thus impossible to conceal. Maybe someone out in the open would be hit if one starts firing unexpectedly. However, the vast majority of cases, the purpose of an automatic gun in war is just to put oatness stream of bullets so that everyone on the other side knows it's stupid to show your head and this allows your own people to move in relative safety because they know where your automatic weapon isn't going to be firing and the enemy, of course, isn't going to be able to respond.