Nexus 2.x had a REST API to download artifacts like below based on some Maven GAV co-ordinates but this no longer works for Nexus 3.x
wget "http://local:8081/service/local/artifact/maven/redirect?g=com.mycompany&a=my-app&v=LATEST" --content-disposition
or
curl --insecure "https://local:8081/service/local/artifact/maven/content?r=public&g=log4j&a=log4j&v=1.2.17&p=jar&c=" > log4j.jar