Like its predecessor, the Zastava M76, the M91 is internally based upon an elongated version of the AK-47 design, but the M91 shares more external similarities with the Dragunov sniper rifle than the M76.

Zastava's website claims that the M91 rifle was designed after a long and careful study of combat tactics and experience of military and police special forces worldwide; and that its development has been carried out under supervision and in close cooperation with some of the most experienced and capable special and anti-terrorist units.

The barrel's bore is chrome-lined for increased corrosion resistance, and features four right-hand grooves with a twist rate of 240 mm (1:9.4 in).

Overall, the design of the flash suppressor, the detachable box magazine, the simplified PSO-type rangefinder reticle used in earlier Zrak telescopic sights, the thumbhole stock and modified bolt carrier as well as a milled receiver strongly point at the Dragunov as the M91's design template.

[5][6] For low light conditions the rifle can also be equipped with PN 5 × 80 passive sights of the first and second generation of night vision devices.