Some more recent data may be found in Appendix A of Commerce in
Firearms in the United States, February 2000 (there through 1998/99).
That report is still available on the ATF web site at:
http://www.atf.gov/pub/fire-explo_pub/020400report.pdf
You'd think a more recent report would have been
the BATFe used to issue this report with address manufacturing data for every gun maker in the country.
Post 9-11 that data is no longer in the report.
in 2000 i was able to re-parse the .pdf data in excel
and change the sort from an alphabetical list to a quantity sort:
heres the top 19 rifle