How Do BFAs Work?

[Clutch]

Kind of a semi-silly question, but how reliable are Walther P99s as converted blank guns? Seems like the only ones I ever see in movies are first-generation models, like the Umarex models in Casino Royale or the QPQ-slide P99s used by Kate Beckinsale in the Underworld movies and Karl Urban in The Bourne Supremacy. I've yet to see any of the 2nd or 3rd-generation models in movies (though Activision and Treyarch modeled one for the Quantum of Solace videogame recently). What's up with that?