Stargate Atlantis is the television series spin-off of Stargate SG-1. It premiered on the Sci-Fi Channel in 2004 and ran for 5 seasons. (This page is dedicated to the real world weapons and some fictional weapons which appear to be based on real world guns. This page does not list completely alien prop weapons.)
The following weapons were used in the television series Stargate: Altlantis:
The FN P90 is the standard submachine gun of the Atlantis expedition as it has been the staple weapon of the Stargate series. It is carried by most Marines and armed scientists including John Sheppard (Joe Flanigan).
Heckler & Koch MP5A3 with Surefire 628 dedicated forend weaponlight and safe-semi-two round burst trigger group - 9x19mmError creating thumbnail: File missingLt. Kagan(Colby Johannson) with an MP5A3 in episode "PHANTOMS".
Heckler & Koch MP5K
The Heckler & Koch MP5K was seen in the hands of a Wraith in season 5, episode 19.
From season 2, Sheppard is seen carrying a Para-Ordnance P-14 over the standard-issue Berettas. The first season he used the Beretta M9 carried by most Atlantis team members.
Ronon uses a specialized pistol that looks like a heavily dressed up revolver. In the story it fires like a phaser, stun and kill with an extra option to blow a huge hole into things. Apparently in the story, the color of the gun changes according to whichever setting. A reddish orange for kill setting or "blow a nasty hole in the wall" setting and white for stun. There is also ammo for this weapon since in scenes where scenes of Ronon reloading his weapon and energy actually drained. In the episode Travelers, the space faring humans were shown with this pistol as their standard sidearm, hinting us that Ronon might have either stolen one and an unthinkable amount of ammo or given one as a present...with an untold amount of ammo. Shepard also pics up one later in that episode and throws it away when it runs out of energy.
Genii pistol - Dressed up Taurus PT99AF aka The Timecop Beretta
In the episode showing the people known as the Genii uses pistols that looked like dressed up Taurus PT99AFs. These are the sidearms first mocked up for the Jean Claude Van Damme Movie Timecop, and previously used in the Stargate SG-1 episode "Icon".
Dressed up Desert Eagle aka the Timecop Desert Eagle
Seen in the hands of the Genii all the time, but never any closeups of what this weapon really is. The video special on weapons of Atlantis reveals it's a heavily dressed up Desert Eagle. It was given a folding a vertical foregrip and sight on top. There is also a special cocking handle to cock the gun since the slide is buried within the dressing. According to the Armorer, Rob Fournier it fires .44 Magnums.
One of these, equipped with an Aimpont sight, is carried briefly by Sheppard in the episode Runner, and is also picked up by Doctor Carson Beckett in the same episode, but is never used.
The GAU-5/A was the USAF contract version of the XM177 "CAR-15" short assault rifle. The real life USAF Security forces used them until recently, however, most of the non firing GAU-5/As seen in both Stargate: SG1 and Stargate: Atlantis were simply XM177E2 "Airsoft guns". No real GAU-5/As were used. All firing guns were mocked up AR15 Heavy Barreled carbines that were cut down and a fake XM177 style flash hider was welded on, and assembled with a registered full auto lower receiver. The Real GAU-5/A carbine did not have a heavy barrel.
Seen used by a few Marines, Major Lorne and notably in one episode by Teal'c and Ronon. Like Teal'c, we'd probably see Ronan with human guns more often, but with his infamous energy pistol blowing up walls, most likely not.
If I remember correctly, in the episode where Ronon(Jason Momoa) and Teal'c(Christopher Judge) used the G36Ks, they randomly switch between G36K and G36KV (without the the 3.5x sight) during the episode.
Seen in the episode "Ghost in the Machine" after/during the part where Dr. Weir walks through the Stargate. Seen in the hands of a enlisted security officer up on an Atlantis balcony.
In episode 19 of season 5, a Wraith that was on Earth, got a hold of a QBZ-97B carbine, a variant of the QBZ-95B made to fire 5.56x45mm and accept STANAG magazines.
Contrary to popular belief, there are no real FN Minimi or M249 light machine guns used in Stargate: Atlantis or its sister show, Stargate: SG1. The light machine guns used by the Atlantis expedition are actually Korean-made Daewoo K3s that have been fitted with M249 Paratrooper-style stocks and shortened barrels, as well as RIS rails and vertical grips similar to those seen on the Mk 46 Mod 0. These weapons were used most notably in the Season 2 episode "Duet" where several were used to shoot down a Wraith Dart.
Winchester Model 1887 Lever Action Shotgun dressed up as a futuristic Gun
These, along with the Taurus PT92s that have a huge sci-fi shroud on them, are guns from the movie TIMECOP, with Jean Claude Van Damme. This is a Winchester Model 1887 lever action shotgun with three fake shotgun barrels on them. It makes it seem like this is a one cock and fire several time, but it could be the trick of camera shots. It isn't clear if this is supposed to be a rifle or a shotgun. This prop was seen used in the 2004 film Blade: Trinity and on the television show Eureka, used by Deputy Jo Lupo.
Like in the previous series, this rocket launcher was misused as an anti air launcher to take out a Wraith Dart. In the following shot, Major Lorne (Kavan Smith) doesn't bother to pop up the sights to fire, which is understandable. The M136 AT4 sights are notorious for being difficult to deploy when the plastic sliding sight covers 'stick', and in the stress of battle, they've been fired a lot just 'point and shoot'.
