[4] Due to political differences between the Soviet Union and Yugoslavia at the time, namely the latter's refusal to join the Warsaw Pact, Zastava was unable to directly obtain the technical specifications for the AK and opted to reverse engineer the weapon type.

Beginning in 1952, Yugoslavia's defence industry had been experimenting with new automatic rifle designs, mostly patterned after the German StG 44, an unknown quantity of which had been captured by Yugoslav Partisans during World War II.

[7] In 1959, two Albanian soldiers defected to Yugoslavia with Soviet AK-47s, which were promptly passed on by the Yugoslav government to be inspected by Zastava engineers.

[7] Zastava was able to make metal castings of the two sample AKs, but could not glean enough technical data to reproduce the weapons or their associated parts.

[7] By the end of the year, however, the Yugoslav government had obtained more early pattern AKs from an unidentified Third World nation that was receiving Soviet military aid.

[8] The first domestic Kalashnikov rifles submitted by Zastava for military field trials were unofficially designated M64 and incorporated a milled receiver based heavily on that of the AK Type 3 but with several cosmetic differences.

[9] As the recoil from the rifle grenade could dislodge the standard AK dust cover, this was replaced with a new design that utilized a spring-loaded bolt.

[8] Both the M70B1 and M70AB2 were fitted with night sights, which alternatively utilized tritium vials or were marked with luminescent paint, that could be raised or lowered as needed.

[8] The addition of the larger trunnions and thicker receivers was seen as a necessary measure to strengthen the rifle design and make it more suitable for launching grenades.

[8] The M64/M70 dust covers were secured into place by a unique locking recoil spring guide, which prevents it from being dislodged while firing rifle grenades.

[8] Zastava began incorporating larger, RPK-pattern barrel trunnions in the M70 during the mid to late 1970s, which resulted in a distinctive bulge on the forward receiver beneath the rifle's bolt handle.

[8] The hook design required a much broader sling swivel to be attached to the M70's gas block than was usual to other Kalashnikov rifles.