Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
firing line [ˈfaɪərɪŋ-] n ли́ния огня́
to be in the firing line (fig) находи́ться*(impf) на ли́нии огня́
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.