Firearm

A firearm, commonly known as a "gun", was a term encompassing a variety of weapons which used a projectile fired from the weapon relying on chemical explosives to propel the projectile at high velocities from the firearm. In the words of Silurian scientist Bokka K'to, "It project[ed] a small piece of metal at high speed." (TV: Doctor Who and the Silurians) They were typically used to penetrate surfaces to maim or kill and were a favoured weapon of humans.

Limitations
Most firearms were ineffective against armoured races such as Daleks and Cybermen, (TV: Army of Ghosts / Doomsday) though specifically designed bullets were produced to take advantage of alien races' weaknesses (Gold in the Cybermen's case). (TV: Battlefield) They were, however, able to penetrate Sontaran space armour. (TV: The Poison Sky) Standard bullets were effective against unarmoured humanoids, such as Weevils, (TV: Exit Wounds) the Ood, (TV: Planet of the Ood), Silents. (TV: Day of the Moon, The Wedding of River Song) Although bullets would not work on armoured races such as the Cybermen and Stingray swarm, rockets and missiles were used to defeat these species. (TV: Doomsday, Planet of the Dead)

As part of the Dalek Project, time travelling bronze Daleks engaged gunmen in battle. (COMIC: The Dalek Project)

Firearms, as a relatively primitive technology, could be neutralised by more advanced technology. For example, Sontaran soldiers employed a cordolaine field that affected metals such as copper, causing weapons using copper casings on their projectiles not to fire. (TV: The Sontaran Stratagem / The Poison Sky)

Technological improvements such as the Bastic bullet made firearms more effective, a viable weapon even against a Dalek. (TV: Revelation of the Daleks, The Parting of the Ways)

UNIT and other military personnel usually used assault rifles and pistols. Officers usually carried pistols or revolvers. In future centuries future soldiers like the Anglican soldiers and soldiers in the Human-Hath War seem to carry a type of assault rifle.

Individuals such as the Doctor and Sarah Jane Smith often refused to use them on moral grounds (TV: Doctor Who, The Stolen Earth, Journey's End, The End of Time, The Doctor's Daughter, Invasion of the Bane) — although there were exceptions. (TV: Pyramids of Mars, The Seeds of Doom, The Time of Angels)

Despite their limitations, humans were known to use firearms well into the 2001st century and beyond. (TV: The Parting of the Ways, Utopia)

An appreciation of the usefulness of firearms was not limited to humanity. Upon landing on the planet Exxilon a Dalek taskforce's weapons were rendered inoperable, forcing them to replace their energy weapons with semi-automatic ballistic weapons. (TV: Death to the Daleks)

Romana II believed guns to have no defensive value. (AUDIO: The Paradox Planet)

Guns were not allowed to be stored at ELF Storage. (TV: Eve of the Daleks)

Availability
Guns were easily obtained in the United States. In Arizona, 2029, the Sixth Doctor joked that they were given away with breakfast cereal. (AUDIO: Shield of the Jötunn)

On Earth, companies existed that manufactured arms. Artemis was an example in the mid-2000s. (AUDIO: Uncanny Valley)

Bolt-action rifle use
John Andrews used a when he chased the Third Doctor and Jo around the deck; Vorg had made the specimens' personalities violent. (TV: Carnival of Monsters)

Laurence Scarman had a hunting rifle which proved ineffective against Sutekh's servitors. Sarah later put the rifle to better use by pulling off a difficult shot to detonate a box of Gelignite that destroyed an Osiran war missile. (TV: Pyramids of Mars)

Lee-Enfield rifles were seen in the hands of the Kaleds and the Thals on the planet Skaro. (TV: Genesis of the Daleks)

Bolt-action rifles were seen in the hands of Hooverville residents. (TV: Daleks in Manhattan)

Assault rifle use
was surrounded by UNIT soldiers from all sides with rifles pointed at him when only one handgun was not sufficient to guard him. This was after he tried to escape capture by stealing Bessie and the Doctor remotely controlled her to drive back to him. (TV: The Dæmons)

Rifles were used to shoot and subdue the Ood on the Ood Sphere. (TV: Planet of the Ood)

The army and UNIT used assault rifles against the Sontarans, Daleks and the Cybermen. They were completely ineffective against the last two. (TV: Army of Ghosts / Doomsday, The Poison Sky, The Stolen Earth / Journey's End)

Gwen Cooper and Ianto Jones used assault rifles to combat a Dalek in the Torchwood Hub. (TV: The Stolen Earth)

's private armed teams fired on the Tenth Doctor, Martha Jones and Jack Harkness with assault rifles. (TV: The Sound of Drums)

Captain Jack led a squad of men to shoot the Toclafane with assault rifles. He also destroyed the Paradox Machine by shooting it with one. (TV: Last of the Time Lords)

The Preachers used a number of automatic weapons to fight the Cybermen, notably the Kalashnikov assault rifle. (TV: Rise of the Cybermen)

Miss Foster's guards were armed with assault rifles. (TV: Partners in Crime)

The security guards in the International Gallery and the police units waiting to arrest Christina de Souza at the end of the tunnel were armed with assault rifles. (TV: Planet of the Dead)

UNIT successfully battled three of the Swarm with assault rifles, although anti-aircraft batteries served a key role in finishing the creatures off. (TV: Planet of the Dead)

Joshua Naismith's private guards were armed with assault rifles, which they employed to put suppressing fire on the Tenth Doctor. (TV: The End of Time)

British Army soldiers were seen armed with assault rifles at the Albion Hospital and in Downing Street. (TV: Aliens of London / World War Three)

US Air Force personnel guarding the Eleventh Doctor at Area 51 were armed with assault rifles. (TV: Day of the Moon)

On Malcassairo, the human guards at Silo 16 repelled the Futurekind with assault rifles. (TV: Utopia)

The crew of the Firebird were equipped with AK-47 assault rifles. (TV: Cold War)

Handgun use
In June 1810, Lord Byron challenged Ryan Sinclair to a duel with pistols and chose his valet Fletcher as his second. (TV: The Haunting of Villa Diodati)

Two fake policemen were in possession of handguns equipped with silencers. (TV: Attack of the Cybermen)

Gustave Lytton gave a handgun to Payne. The Sixth Doctor took it after his death and Russell took it when he arrested the Doctor. (TV: Attack of the Cybermen)

Brigadier Lethbridge-Stewart and members of UNIT threatened with handguns. (TV: The Claws of Axos)

The Lorduke of Zazz threatened Frobisher with a handgun. (COMIC: The Gift)

When the lone Dalek, also known as the Metaltron, escaped the Vault, the security guards used pistols against it, to no effect. (TV: Dalek)

Jo Grant brandished a revolver when tracing to Devil's End. (TV: The Dæmons)

When Eva Saint Julienne was promoted to Floor 500, she pulled a pistol on the Editor. She fired the pistol at the Jagrafess, to no effect. (TV: The Long Game)

Jack Harkness used a 21st century era pistol against the Daleks invading the Game Station. (TV: The Parting of the Ways)

Queen Victoria carried a small revolver in her bag for her protection. She shot Father Angelo with it. (TV: Tooth and Claw)

Maximillian Stael committed suicide with a handgun given to him by the Fourth Doctor at his behest. He did this to avert the Fendahl from using him as a power source. (TV: Image of the Fendahl)

Jake Simmonds and Mrs. Moore pulled pistols on Mickey Smith when they found out he wasn't Ricky Smith. (TV: Rise of the Cybermen)

Tallulah had a prop handgun to scare the Tenth Doctor, Martha Jones and Solomon. (TV: Daleks in Manhattan)

's henchmen pulled out pistols to everyone witnessing when the Toclafane killed President Winters. (TV: The Sound of Drums)

Thomas Milligan used a handgun to lure a Toclafane to the trap set up by Alison Docherty. Lucy Saxon used one to kill. (TV: Last of the Time Lords)

Jack Harkness carried a revolver while in service with Torchwood. (TV: Everything Changes)

General Cobb intended to shoot the Tenth Doctor with a handgun but Jenny got in the way. (TV: The Doctor's Daughter)

Colonel Mace shot Commander Skorr with a handgun. (TV: The Poison Sky)

General Sanchez attempted to repel the invading Dalek with a handgun. (TV: The Stolen Earth)

A German woman threatened Martha Jones with a Luger in an attempt to prevent her from using the Osterhagen Key, but lowered the pistol when she proved unable to kill her. (TV: Journey's End)

John Jefferson shot an Ood with a handgun. He only fired one shot. (TV: The Satan Pit)

The Fourth Doctor took Scorby's handgun and used it to retreat in safety. He told Sarah he'd never use it but they didn't know that. (TV: The Seeds of Doom)

Captain Erisa Magambo threatened Malcolm Taylor with a pistol, and later used it to defend against three of the Swarm. (TV: Planet of the Dead)

Wilfred Mott took his old service revolver with him when he sought out the Tenth Doctor. He later gave it to the Doctor, who took it to use against the Master. The Doctor had to choose between shooting the Master or Rassilon, but finally chose to shoot the White-Point Star, destroying it and breaking the link that anchored the Time Lords in the present time, sending them back into the Time War and saving the universe. (TV: The End of Time)

The Fifth Doctor used a handgun against a Dalek mutant that had escaped from its damaged armour. He decided that he needed to kill Davros but when the moment came he couldn't bring himself to pull the trigger. (TV: Resurrection of the Daleks)

The Sixth Doctor used an automatic pistol against a Dalek's eye stalk. (TV: Revelation of the Daleks)

Both the Seventh Doctor and Ace used a handgun to protect themselves from Josiah Samuel Smith (TV: Ghost Light).

The Eleventh Doctor fired a handgun to destroy a gravity globe. (TV: The Time of Angels / Flesh and Stone)

Amy Pond used Canton Everett Delaware III's handgun on a little girl in an astronaut suit, not knowing she was her daughter Melody, in an attempt to save the Eleventh Doctor. (TV: The Impossible Astronaut, Let's Kill Hitler)

The War Master shot Liv Chenka multiple times with a handgun. She later shot him in the arm. (AUDIO: Day of the Master)

Machine gun, submachine gun and PDW use
Machine guns were carried by the Robomen during the Daleks' invasion of 22nd century Earth. (TV: The Dalek Invasion of Earth)

Inside the Miniscope, the crew of the SS Bernice used submachine guns against the Drashigs to no avail. (TV: Carnival of Monsters)

Gustave Lytton had a silenced submachine gun. (TV: Attack of the Cybermen)

Mounted machine guns were used to shoot the Scarecrow Drones when they attacked the Farringham School for Boys. They trained with these in the school grounds. (TV: The Family of Blood)

Harrison Chase's guards all carried submachine guns. (TV: The Seeds of Doom)

The crew of a Delta III refinery had two machine guns. (TV: The Power of Kroll)

The use of other firearms
The Fourth Doctor used an Oriental fowling piece belonging to George Litefoot to kill a giant rat when it attacked Leela. The gun hadn't been fired for 50 years and Litefoot warned the Doctor that it would probably explode in his face. The Doctor scoffed at this, saying that the gun had been built in Birmingham.(TV: The Talons of Weng-Chiang)

When one of the Fendahleen was feeding on the psychic energy of Leela and the Tylers, the Fourth Doctor tried to distract it by shooting it with Jack Tyler's double-barreled shotgun filled with rock salt. Leela later used the shotgun to kill another of the Fendahleen. (TV: Image of the Fendahl)

After the Twelfth Doctor returned to Gallifrey, Rassilon's firing squad were ordered to shoot him, but purposefully missed. They then sided with the Doctor, dropping their guns and standing at his side. Last to join him was the Eleventh General who dropped his pistol after telling Rassilon "Lord President, with respect, get off his planet." Desperate to save Clara Oswald, the Doctor stole the General's gun and threatened him with it. The General told him it was the side arm of the Personal Guard of the Lord President and had no stun setting. After making sure the General could still regenerate, the Doctor shot him in the chest and fled with Clara. The General then regenerated into a woman, his preferred form. (TV: Hell Bent)

Behind the scenes

 * Most firearms used in the 2005 series are of manufacture, specifically G36 assault rifles and USP sidearms. Glocks and Webleys have also been used.
 * The guns carried by Sanctuary Base 6 security in The Impossible Planet / The Satan Pit are fitted with suppressors (the same model of weapon commonly associated with  universe).
 * In the various UNIT episodes during the Jon Pertwee era, or  were used.