THE SAMPLES WERE SENT TO 165 LABORATORIES, 130 OF WHICH RESPONDED WITH COMPLETED DATA SHEETS. THE SAMPLES WERE ACCOMPANIED BY THE EXPLANATION THAT TWO HOMICIDES HAD OCCURRED, APPROXIMATELY 10 DAYS APART, AND THAT ONE PROJECTILE AND ONE CARTRIDGE CASE HAD BEEN RECOVERED FROM THE FIRST HOMICIDE SCENE AND THAT TWO PROJECTILES AND ONE CARTRIDGE CASE WERE FROM THE SECOND HOMICIDE SCENE. THE LABORATORIES WERE TO DETERMINE WHICH, IF ANY, OF THE THREE BULLETS HAD BEEN FIRED FROM THE SAME GUN, AND WHETHER THE TWO CARTRIDGE CASES CAME FROM THE SAME GUN. OF THE 130 LABORATORIES RETURNING DATA, 124 (95.4 PERCENT) ANSWERED THE QUESTION ABOUT THE PROJECTILES IN A WAY THAT IS CONSISTENT WITH THE SAMPLE SUPPLIER'S STATEMENT REGARDING THE GUN FROM WHICH THE BULLETS WERE FIRED, AND 101 (77.7 PERCENT) CORRECTLY CONCLUDED THAT THE CARTRIDGE CASES HAD NOT FIRED IN THE SAME GUN. A TABULAR BREAKDOWN OF RESPONSES FROM EACH LABORATORY IS INCLUDED. UNLIKE ANOTHER LABORATORY PROFICIENCY TEST INVOLVING FIREARMS EVIDENCE (NCJ-475523), NO INFORMATION ON THE ANALYTICAL METHODS USED BY THE LABORATORIES IS INCLUDED. EXPLANATION OF THE SURVEY METHOD AND A COPY OF THE QUESTIONNAIRE ARE PROVIDED. OTHER PROFICIENCY TESTS INVOLVING FIREARMS EVIDENCE ARE DOCUMENTED IN NCJ - 47542. TESTS INVOLVING OTHR KINDS OF EVIDENCE ARE REPORTED IN NCJ-47522, 47524-47527, AND 47529 - 47541. (LKM)