ic ▁conditions ▁and ▁target ▁eng agement ▁ranges , ▁while ▁using ▁the ▁same ▁guns ight ▁aim point . ▁ ▁Tra ject ory ▁match ▁is ▁not ▁intended ▁to ▁be ▁perfect , ▁an ▁engineering ▁impos s ibility ▁under ▁the ▁closest ▁of ▁similar ities ▁between ▁the ▁two ▁bul lets , ▁that ▁is ▁further ▁complicated ▁in ▁the ▁case ▁of ▁the ▁trac er ▁losing ▁mass ▁and ▁changing ▁its ▁drag ▁properties ▁as ▁it ▁f lies . ▁ ▁The ▁intent ▁is ▁that ▁the ▁trac er ▁matches ▁the ▁ball ▁round ▁well ▁enough ▁for ▁the ▁purposes ▁of ▁mach in eg un ▁fire . ▁ ▁The ▁M 8 5 6 ▁trac er ▁cart ridge ▁( 6 3 . 7 - gra in ▁bullet ) ▁is ▁used ▁in ▁the ▁M 1 6 A 2 / 3 / 4 , ▁M 4 - series , ▁and ▁M 2 4 9 ▁weapons ▁( am ong ▁other ▁ 5 . 5 6 mm ▁NAT O ▁weapons ). ▁This ▁round ▁is ▁designed ▁to ▁trace ▁out ▁to ▁ 8 7 5 ▁yards ▁and ▁has ▁an ▁orange ▁tip ▁color , ▁and ▁is ▁traject ory ▁matched ▁to ▁the ▁M 8 5 5 ▁( 6 2 - gra in , ▁green ▁tip ) ▁ball ▁cart ridge . ▁ ▁The ▁M 8 5 6 ▁trac er ▁should ▁not ▁be ▁used ▁in ▁the ▁M 1 6 A 1 ▁except ▁under ▁emer gency ▁conditions ▁and ▁only ▁in ▁relatively ▁warm ▁weather , ▁because ▁the ▁M 1 6 A 1 ' s ▁slower ▁ 1 : 1 2 ▁rif ling ▁tw ist ▁is ▁not ▁sufficient ▁to ▁properly ▁stabil