DS Jim Bergerac (John Nettles) holds a Smith & Wesson Military & Police (or maybe a Victory Model) revolver with 4" barrel during the training counter-terrorist operation in the opening scene in "A Message for the Rich" (S02E01). Same looking revolvers are seen in hands of police officers in the final scene of the same episode. A Smith & Wesson M&P revolver with 5" barrel is seen in "Prime Target" (S02E04) as a part of Lionel Carteret's gun collection.
Colt Trooper Mk III
A Colt Trooper Mk III is the murder weapon in "Prime Target" (S02E04). In the opening scene the revolver is used by Duchesne's henchman Raoul (Stephen Lawrence). Later Duchesne (Constantine Gregory) orders Raoul to hide the revolver in Veronique's house where it is found by police. The revolver, used by Lionel Carteret (Anthony Valentine) in the climactic scene, is also the Colt Trooper, and most likely the same prop, though according to the plot it must be the Smith & Wesson Military & Police that is seen in Carteret's gun collection (see above).
Unidentified revolvers
Revolvers are seen in hands of police officers in "A Message for the Rich" (S02E01) and "Clap Hands, Here Comes Charlie" (S02E03). Mostly this guns are seen very briefly and hardly can be identified.
Pistols
Walther P38
A Walther P38 is seen in Carteret's gun collection in "Prime Target" (S02E04).
Flintlock Pistol
Two Flintlock Pistols are seen in Carteret's gun collection in "Prime Target" (S02E04). One of them is a Model 1806 New Land Pattern, another is seen only partially and the exact model cannot be identified.
Percussion Cap Pistol
A Percussion Cap Pistol is seen in Carteret's gun collection in "Prime Target" (S02E04).
Colt Thuer Derringer
A Colt Thuer Derringer is seen in Carteret's gun collection in "Prime Target" (S02E04).
Unidentified handguns
Some more handguns in Carteret's gun collection are seen only partially.
Rifles
Takedown M1 Carbine
The hitman Georges Giroux (Denis Lawson) uses a takedown M1 Carbine with sniper scope and sound suppressor in "A Miracle Every Week" (S02E07). This rifle together with the scope and the suppressor looks the same as the gun in 1979 British film Love and Bullets.