In the climactic scene in "The Jackdaw's Revenge" (S06E02) Father Brown (Mark Williams) picks up a Webley .38 Mk IV revolver; then it is taken from him by Eddie Hamsley (Katie Buchholtz) and at last falls in hands of Robin Gladwell (Paul Cawley). Another Webley (possibly same prop reused) is hold by tied Bunty Windermere (Emer Kenny). Webley revolvers, most likely also .38 Mk IV, are briefly seen, used by MI5 operatives in "The Face of the Enemy" (S06E05). In "The Flower of the Fairway" (S06E09) Hermione Harvey (Jane Hazlegrove) uses her late husband's Webley Mk IV to pistol-whip a strange man hanging around her garden.
Webley .455 Mk VI
A Webley .455 Mk VI revolver is seen next to dead body of Eric Worcester (Adam Kotz) in "The Devil You Know" (S06E06).
Pistols
Walther PPK
In "The Face of the Enemy" (S06E05) Benedict Northam (Richard Harrington) carries a Walther PPK. His pistol is later used by Lara Winslow (Mary Antony) and then returns to Northam.
Beretta M1951
In "The Face of the Enemy" (S06E05) an uncredited hitman uses a suppressed Beretta M1951 pistol. In "The Two Deaths of Hercule Flambeau" (S06E10) Beretta M1951 pistols are used by Hercule Flambeau (John Light), Lisandra Flambeau (Sara Martins), and Order of Malta knights, guarding the Iron Crown of Lombardy.
Browning Hi-Power
MI5 agent Daniel Whittaker (Daniel Flynn) carries a Browning Hi-Power pistol in "The Face of the Enemy" (S06E05). The Hi-Power appears to be a "Type 73" model, anachronistic for mid-1950s.
Walther P38
In the climactic scene in "The Devil You Know" (S06E06) Christina Worcester (Éva Magyar) uses a Walther P38.