▁direction ▁of ▁fire , ▁trac er ▁r ounds ▁can ▁also ▁be ▁loaded ▁at ▁the ▁end ▁of ▁a ▁magazine ▁to ▁alert ▁the ▁shoot er ▁that ▁the ▁magazine ▁is ▁almost ▁empty . ▁This ▁is ▁particularly ▁useful ▁in ▁weapons ▁that ▁do ▁not ▁lock ▁the ▁b olt ▁back ▁when ▁empty ▁( such ▁as ▁the ▁A K - 4 7 ). ▁During ▁World ▁War ▁II , ▁the ▁Soviet ▁Air ▁Force ▁also ▁used ▁this ▁practice ▁for ▁aircraft ▁machine ▁guns . ▁One ▁dis adv antage ▁in ▁this ▁practice ▁is ▁that ▁the ▁enemy ▁is ▁alert ed ▁that ▁the ▁pilot ▁or ▁shoot er ▁is ▁low ▁on ▁am mun ition ▁and ▁possibly ▁vulner able . ▁For ▁ground ▁forces , ▁this ▁generally ▁offers ▁no ▁tact ical ▁advantage ▁to ▁the ▁enemy , ▁since ▁a ▁soldier ▁with ▁a ▁crew - ser ved ▁weapon ▁such ▁as ▁a ▁machine ▁gun ▁who ▁is ▁out ▁of ▁am mun ition ▁is ▁supposed ▁to ▁alert ▁his ▁team ▁that ▁he ▁is ▁" d ry " ▁and ▁rely ▁on ▁their ▁cover ▁fire ▁while ▁he ▁re loads ▁the ▁machine ▁gun . ▁Thus , ▁an ▁enemy ▁must ▁risk ▁expos ing ▁himself ▁in ▁order ▁to ▁attack ▁the ▁re loading ▁soldier . ▁Modern ▁jet ▁f igh ters ▁primarily ▁rely ▁on ▁rad ar ▁and ▁inf ra red ▁see ker ▁miss iles ▁to ▁track ▁and ▁destroy ▁enemy ▁plan es ▁and ▁las er - gu ided ▁miss iles ▁to ▁attack ▁surface ▁targets , ▁rather ▁than ▁the ▁plane ' s ▁can non , ▁which ▁may ▁be ▁just ▁an ▁anc ill ary ▁weapon ▁for ▁air - to - air ▁combat ; ▁although ▁in