▁W C ▁ 8 4 6 ▁pow der . ▁The ▁trac er ▁comp ound ▁contains ▁composition ▁R ▁ 2 8 4 ▁which ▁is ▁ 1 7 % ▁poly vin yl ▁ch lor ide , ▁ 2 8 % ▁mag nes ium ▁pow der , ▁and ▁ 5 5 % ▁str ont ium ▁nit rate . ▁( This ▁is ▁the ▁same ▁composition ▁used ▁on ▁the ▁M 1 9 6 .) ▁ ▁The ▁M 2 7 6 ▁is ▁a ▁vio let - ti pped ▁ 7 . 6 2 × 5 1 mm ▁NAT O ▁dim ▁trac er ▁that ▁uses ▁composition ▁R ▁ 4 4 0 , ▁which ▁is ▁b arium ▁per ox ide , ▁str ont ium ▁per ox ide , ▁calci um ▁res inate ▁for ▁example ▁calci um ▁ab iet ate , ▁and ▁mag nes ium ▁carbon ate . ▁ ▁T rac er ▁compos itions ▁can ▁also ▁emit ▁primarily ▁in ▁inf ra red , ▁for ▁use ▁with ▁night - vision ▁devices . ▁An ▁example ▁composition ▁is ▁bor on , ▁pot ass ium ▁per ch lor ate , ▁sod ium ▁sal ic yl ate , ▁iron ▁carbon ate ▁or ▁mag nes ium ▁carbon ate ▁( as ▁comb ust ion ▁ret ard ant ), ▁and ▁b inder . ▁Many ▁variants ▁exist . ▁ ▁Other ▁applications ▁▁ ▁T rac ers ▁can ▁also ▁serve ▁to ▁direct ▁fire ▁at ▁a ▁given ▁target , ▁because ▁they ▁are ▁visible ▁to ▁other ▁combat ants . ▁The ▁dis adv antage ▁is ▁that ▁they ▁bet ray ▁the ▁gun ner ' s ▁position ;