Just trying to delete all the documents, and did this:
http://localhost:8983/solr/update?stream.body=%3Cdelete%3E%3Cquery%3E*:*%3C/query%3E%3C/delete%3E <
http://localhost:8983/solr/update?stream.body=%3Cdelete%3E%3Cquery%3E*:*%3C/query%3E%3C/delete%3E
Put the commit=true parameter in you GET request:
http://localhost:8983/solr/update?stream.body=%3Cdelete%3E%3Cquery%3E*:*%3C/query%3E%3C/delete%3E&commit=true