NYPD Detective's Javier Esposito (Jon Huertas) and Kevin Ryan (Seamus Dever) use a Glock 17 as their primary sidearms throughout the series. Detective Kate Beckett (Stana Katic) uses one until "Home is Where the Heart Stops". Criminals also like them, one was used with a suppressor to murder Roger Farraday (Dean Cates) in A Deadly Game.
Error creating thumbnail: File missingGlock 17 - 9x19mmError creating thumbnail: File missingBeckett taking cover with her Glock 17, this is almost certainly an airsoft gun, notice the seam running up the bottom of the gun, as well as the lack of the metal serial number insert. - Episode: Always Buy RetailError creating thumbnail: File missingRyan (Seamus Dever) holding his Captain (Not visible in this frame), rather than the suspect at gun point. - Episode: Kill the MessengerError creating thumbnail: File missingEsposito's Glock jams as he fires on a murder suspect. A moment later he's seen clearing it, rather than handing it off for a functioning spare. - Episode: A Deadly AffairError creating thumbnail: File missingThe killer takes aim. - Episode: A Deadly Game. It is in fact a Glock 17 pictured, though the coroner concluded the victim was killed by someone using a .45, and at the end of the episode the killer was accused of using a ".45 Glock".
Glock 19
Detective Kate Beckett (Stana Katic) starts carrying the more compact Glock 19 during the events of "Home is Where the Heart Stops". Castle (Nathan Fillion) also uses Kate's while at the range, pretending to be completely inexperienced, then showing extreme proficiency after he's offered crime scene photos. Det. Tom Demming (Michael Trucco) also carries one.
A Glock 26 serves as Det. Beckett's backup gun, it's most notably seen when she hands it to Castle to defend himself from the "Tick, Tick, Tick..." & "Boom!" killer when they enter the warehouse he's hiding in. He uses it to shoot Kate's Glock 19 out of the killers hand. After wards Castle reveals that "he was aiming for his head". Castle again uses Kate's Glock 26 in order to defend himself in the season 3 premiere A Deadly Affair, he uses it to wound a gunman who came up behind Beckett.
Noteworthy is that his "Aiming for the head" remark is the third Firefly/Serenity reference in the series. The first two took place during the episode "Vampire Weekend" when Castle wore his Mal costume, and the second was a catalyst sitting on his bookshelf. A catalyst is required for any Firefly class ship to run, and was a large part of Out of Gas' story arc.
Noel du Preez (Michael Enright) uses a compensated 1911 to shoot at the team when he thinks they're robbers stealing from his store. Former NYPD officer, and Esposito's former partner Ike Thornton (Aaron D. Spears) is seen with a 1911 during Den of Thieves, off camera Esposito uses it to wound dirty IA Lt. Holliwell. A 1911 is found to be the murder weapon in the season 3 premiere. A murder suspect named Roland D'Andre (Randal Reeder) is found to have a Safari Arms Matchmaster 5 on him.
The "Tick, Tick, Tick..." & "Boom!" killer uses this during his activities in "Boom!", FBI Special Agent Jordan Shaw (Dana Delany) briefly uses it near the end of the same episode.
Gayle Carver (Sophina Brown) is seen wielding this gun during a confrontation between the detectives, Mike Royce (Jason Beghe) and Clifford Stuckey (James Handy).
Montgomery uses a Bond Arms Snake Slayer IV Derringer as his holdout weapon during his confrontation with Lockwood in "Knockout". It is the IV version of the Snake Slayer as noted by its longer barrel, and although normally chambered in .45 this pistol appears to use the .38/.357 barrel, as Montgomery loads it with the same rimmed rounds he uses in his revolver.
Castle is seen wielding one while bursting through his front door and catching his daughter snogging her boyfriend. Irwin Finkelstein is seen holding two antique revolvers in pictures on a antique firearms social networking page.
In Punked, Daniel Goldstein and Adam Murphy are found to have each used flintlock pistols in a duel to impress a woman. Later, while trying to determine whether to charge Adam with murder or manslaughter, they hilariously succeed at hitting everything in the range but the targets. After several failed attempts, Castle uses duct tape to attach a scope, and laser sight in a last ditch attempt to hit the target. Other models are also seen being held by Ivan Podofski (Muse Watson) in photos on a antique firearms social networking page.
Detectives arrive at the crime scene to find a female victim with multiple flat-head nails protruding from her skull. Behind a nearby chair they find a nail gun. It appears to be a cosmetically altered KitPro series judging by the shape of the butt, housing assembly (screws pointing aft), housing vents on the side and top, and the 'over/under' 'muzzle'. I think the 'over' is a nail depth gauge.
Submachine Guns
Heckler & Koch MP5A4
An MP5A4 with a weapon light, and Navy trigger group was used by a drug dealer while stealing a victims body in the season 2 premiere, "Deep in Death".
During the events of "A Deadly Game", an MP5K is found in Roger Farraday's (Dean Cates) car. It was issued to him as part of a "spycation" where Farraday, under the guise of CIA hitman Sean Caldwell, was supposed to "assassinate" a foreign minister with it.
Esposito (Jon Huertas), as well as most NYPD ESU officers use M4A1's when needed. FBI HRT agents can be seen wielding both M4A1's and HK416's during the episodes "Tick, Tick, Tick..." & "Boom!".
Esposito (Jon Huertas) uses a Remington 870 on multiple occasions throughout the season. In Sucker Punch, the victim Jack Coonan (Justin Alvarez) had one loaded with hollow point slugs in his apartment.
Mike Royce (Jason Beghe) is seen wielding what appears to be a Mossberg 500AT shotgun during a confrontation between the detectives, Gayle Carver (Sophina Brown) and Clifford Stuckey (James Handy).
Hal Lockwood (Max Martini) uses a suppressed Mk 14 EBR kill John Raglan, and later attempts to kill Beckett with it. It appears to have a Harris bipod and AN/PEQ-2/5. It is supposedly chambered in .338, despite the round being much too large for fit the 7.62x51mm chamber.
A Knight's Armament SR-25 can be seen in "Rise". It is recovered after the attempted assassination attempt on Becket. Esposito refers to it as a Mk 11, which is correct as this particular rifle was a Navy SEAL issue weapon.
