Can't seem to get any kills in Matchmaking games

Hey all. sorry if this is a stupid question but here goes… When I am in multiplayer modes I can’t seem to get many kills. I can dump a whole clip 20+ into a guy and he doesn’t drop. Is this just because he has good armor? Seems like i’m missing something basic here. Also I seem to get killed alot by one melee bash and I can hit a guy several times and not drop him… TIA

Use a headshot weapon, and shoot him in the head with hit 5 times to get a kill. AR only works if is basically 3 inches away from you.

Stop missing.