The unregistered weapons were handed over to the authorities as the government vows to disarm the country after two mass shootings.
Eight children and a security guard were killed by a 13-year-old boy who entered a school in the Serbian capital armed with pistols owned by his father.
Fierce fighting has yielded heavy casualties but little movement. Ukrainian forces need heavy weapons to change that, but they say it is no guarantee.
People who would not be allowed anywhere near the battlefield in a U.S.-led war are active on the Ukrainian front, with ready access to American weapons.