Raymond Worrall's (Benjamin Fisher) Smith & Wesson Victory Model, identified by dull grey parkerized finish, plain wooden grips and lanyard ring, is the murder weapon in "The Eagle and the Daw" (S05E06).
Smith & Wesson Military & Police
The Smith & Wesson Military & Police is found on the place of murder in "The Tanganyika Green" (S05E13). In the flashback scene it is seen in hands of Wynford Collins (Miles Jupp).
Unidentified revolver (Smith & Wesson Sawed-Off?)
In "The Sins of Others" (S05E11) Sid Carter (Alex Price) owns an illegally purchased snub nose 6-shot revolver. In some scenes Penelope "Bunty" Windermere (Emer Kenny) and Lydia Reese (Susie Trayling) briefly hold Sid's revolver. The gun looks S&W style, with thumb cylinder release, unsupported ejector rod, large grip with lanyard ring, but lacks front sight. A possible guess is a standard Smith & Wesson revolver, like Military & Police Model that has the part of the barrel with ejector rod socket sawed-off. Same looking revolver, probably same prop reused, is seen in Season 7.
Shotguns
Double Barreled Shotgun
Two Double Barreled Shotguns are seen in the locker in Frank Hammond's workshop in "The Tanganyika Green" (S05E13). John Hammond (Bradley Hall) takes one of these guns. Peggy Hardwick (Emma Pallant) uses the double barreled shotgun in "The Penitent Man" (S05E15) until she is disarmed by Flambeau (John Light) who in turn hands the shotgun to Bunty Windermere (Emer Kenny).
Rifles
Mauser 98 Sporter
In "The Sins of Others" (S05E11) the assassin, credited as "Panama Man" (James Sutherland), uses a rifle with sniper scope and sound suppressor. It is possibly some version of Mauser 98 Sporter.
Lee-Enfield No.4 Mk.I
In the final scene in "The Penitent Man" (S05E15) the prison guard Terry Mitchell (Dylan Brown) uses the Lee-Enfield No.4 Mk.I. The rifle has square box magazine so it appears to be converted for 7.62x51mm NATO caliber.
Other Weapons
Pellet Gun
In the scene on the village fair in "The Tanganyika Green" (S05E13) a local gentleman shoots a pellet gun.