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The Glock 17 is seen used prominently in the film. Floyd Lawton/Deadshot (Will Smith) uses a heavily customized Glock 17 with a compensator and red dot sight. Several Special Forces soldiers, in addition to Rick Flag, carry unmodified Glock 17s.
Glock 18
Besides his custom Glock 17 and his wrist guns, Deadshot (Will Smith) carries two full-auto Glock 18s in duel small-of-the-back holsters.
Harley Quinn (Margot Robbie) carries an ornately decorated Chiappa Rhino 60DS. The revolver has white grips inlaid with a gold Joker emblem, gold decoration on the barrel shorud, and the cylinder has alternating "Love"/"Hate" gold decoration. The revolver is seen also in the hands of Deadshot.
Custom Colt Gold Cup Trophy
The Joker (Jared Leto) carries a custom Colt Gold Cup Trophy as his primary sidearm. It is heavily customized with a purple finished slide and frame with all the other parts being gold plated, custom gold inlaid engravings on the flats of the slide and frame, and textured faux ivory grip panels with gold Joker emblems.
Rifles/Carbines
Heckler & Koch HK416
Rick Flag (Joel Kinnaman) carries a Heckler & Koch HK416 fitted with a Geissele Automatics 14.5 Super Modular Rail handguard. The rifle looks to be equipped with Gen 1 Magpul AFG, AN/PEQ-15 Laser Designator, and a Leupold Mark 6 1-6x20mm M6C1 rifle scope with an Aimpoint T2 Red Dot attached on the right side of the scope.
Daniel Defense DDM4 MK18
Several of the US Navy SEALs and Special Forces soldiers who accompany the Suicide Squad including Lt. GQ Edwards (Scott Eastwood) can be seen with Daniel Defense DDM4 MK18 carbines fitted with various accessories. Floyd Lawton/Deadshot (Will Smith) is seen loading up a DDM4 Mk18 fitted with a Troy PDW stock, canted back up iron sights, and an EOTech XPS sight.
Deadshot's Custom AR-15
Floyd Lawton/Deadshot (Will Smith) carries a custom AR-15. The rifle has a two tone red and gold paintjob, has a red painted Magpul CTR stock, and is fitted with a custom made handguard and muzzle brake. The rifle is also fitted with an ACOG (with custom gold finish) with an Trijicon RMR Sight (Adjustable LED) mounted on top, along with a vertical grip. Deadshot also uses customized magazines, which are red painted Magpul PMAGs fitted with gold finished TTI Firepower magazine extensions (these are replacement PMAG baseplates which increase the capacity of a 30 round magazine to 35 rounds).
M4A1
Guards escorting Killer Croc (Adewale Akinnuoye-Agbaje), as well as an armed assailant wearing a Batman mask, are seen carrying M4A1s.
AKM
A heavily customised AKM with a suppressor is seen used by one of the Joker's armed assailants, who is dressed in a Panda suit.
The Browning M2HB is seen mounted on Humvees throughout the film.
M60
An M60 (with the bipod removed) is used by one of the Joker's men.
Mk 48 Mod 0
A Mk 48 Mod 0 is carried by one of the Navy SEALs accompanying Task Force X.
Other
M72 LAW
An M72 LAW is seen being fired by a Special Forces soldier during the city ambush.
Deadshot Wrist Weapons
Deadshot is also armed with dual wrist weapons that are built from Glock pistols.
The Joker's Arsenal
In one scene, the Joker is seen lying amongst a collection of knives and firearms, which appear to contain many pistols including what appears to be an IWI X95.