Here is what 23 CFR the International Traffic in Arms Regulation says about exporting brass from the U.S. If you look at the definitions you will find brass is defined as a component of Ammunition.

Sect 123.17 .Exports of firearms and ammunltlon.
(a) Except as provided in Sect 126.1 of
this subchapter, District Directors of
Customs shall permit the export without
a license of components and parts
for Category I(a) firearms, except barrels,
cylinders, receivers (frames) or
complete breech mechanisms when the
total value does not exceed $100 wholesale
in any transaction.

That will get it out of the U.S. Then you will have to figure out how to get into the other country.

Section 126.1 refers shipping to prohibited countries.