Deckard's Pfläger-Katsumata Series D 5223

https://youtube.com/shorts/p_5AGcU5AUk

Yep there's no lore about that pistol in Blade Runner. And it was made out of a real world revolver and a bolt action rifle. It's just supposed to be a gun that has multiple shots and a lot of stopping power to retire a replicant in one shot.