Unluky robber Daryl Cudlip (Andrew Turner) uses a snub nose revolver during the robbery of Dame Bianca Norman's pullman wagon in "The Great Train Robbery" (S07E01). 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. A revolver with same outlook, most likely same prop, is seen in Season 5.
Webley .38 Mk IV Duty Model
Daryl Cudlip's brother Lenny (Darryl Clark) uses a Webley .38 Mk IV Duty Model during the robbery in "The Great Train Robbery" (S07E01). A Webley .38 Mk IV Duty is seen next to dead Lionel (uncredited) in "The Blood of the Anarchists" (S07E08). In flashback scene this revolver is in hands of Angus Boyde (Kevin Mains).
Webley .455 Mk VI
Constable Colin Blaisen (Reis Bruce) holds a Webley .455 Mk VI in several scenes in "The Sacrifice of Tantalus" (S07E06).
Enfield No.2 Mk.1*
Edmund Noon (Billy Postlethwaite) holds a Enfield No.2 Mk.1* in flashback scene in "The Darkest Noon" (S07E05).
Pistols
Walther PPK
A Walther PPK is the murder weapon in "The Great Train Robbery" (S07E01).
Browning Hi-Power
In "The Sacrifice of Tantalus" (S07E06) Special Branch Inspector Sullivan (Tom Chambers), acting under the name of Inspector Trueman, carries a Browning Hi-Power. He then hands his pistol to Chief Superintendent Len Blaisen (Sean Gallagher). This gun has "Type 73"-style hammer spur and non-standard wide vertical slide serration, like Hi-Power pistols, seen in Seasons 3 and 4. Possibly this is some modern blank firing replica.
Rifles
Lee-Enfield No.1 Mk.III*
During the police operation to arrest Cudlip brothers in "The Great Train Robbery" (S07E01) Inspector Mallory (Jack Deam) and Sergeant Goodfellow (John Burton) are armed with Lee-Enfield No.1 Mk.III* rifles. Jimbo Riley (James Cartwright) holds a No.1 Mk.III* rifle in "The Demise of the Debutante" (S07E04).
Lee-Enfield No.4 Mk.I
Four constables are armed with Lee-Enfield No.4 Mk.I rifles in said scene in "The Great Train Robbery" (S07E01). Some of these rifles have angular magazines, indicating that they are chambered in 7.62x51mm NATO.