I find it slightly worrying that a university can let you get to the 'hands-on' stage in your training without having provided you with a list of the standard reference works for each of the various disciplines within forensic science. You need to lay your hands on a copy of Jane's Guns Recognition Guide:
http://www.amazon.co.uk/exec/obidos/ASIN/0007183283/qid= 1133468195/sr=1-1/ref=sr_1_8_1/202-9177319-2601414
Alternatively, you could try showing some photographs of the weapon to a local gun dealer. (Just look in Yellow Pages).
Chris