0000902584-04-000047 SC 13G 1 20040217 AMERICAN PACIFIC CORP 0000350832 2810 596490478 DE 0930 SC 13G 34 005-33521 04601778 3770 HOWARD HUGHES PKWY STE 300 LAS VEGAS NV 89109 7027352200 3770 HOWARD HUGHES PKWY STE 300 3770 HOWARD HUGHES PKWY STE 300 LAS VEGAS NV 89109 ADVISORY RESEARCH INC 0000902584 0000 132831881 DE 1231 SC 13G 180 N. STETSON STREET STE 5780 CHICAGO IL 60601 3125651414 180 N. STETSON STREET SUITE 5780 CHICAGO IL 60601 SC 13G 1 aripac.txt AMERICAN PACIFIC CORP SCHEDULE 13G