Definition of be firing (or shooting) blanks in US English:

be firing (or shooting) blanks

phrase

informal
  • (of a man) be infertile.

    • ‘He's probably been firing blanks for years, but wouldn't admit it for a second - after all, a man isn't really a man if he can't hit the target.’
    • ‘Will my princess be disappointed when she discovers I am firing blanks?’