It's a logo of a pointed bullet still in it's casing. The casing is much larger than the bullet as is common in a high powered rifle. The rectangular shaped casing has a little glint of light on it making it look like it is shiny.
Related to Ammo Icon
Related icons are the icons with matching tags, as well as all military icons. All icons are in the same flat style. You can either download free PNG icons or buy SVG vectors