The rifle used in the assassination attempt is named in the series as a "Black King". In "Killing Zone" (S1E06), it is described as one of four rifles in the world powerful enough to use the special round designed by Swagger's instructor Rathford O'Brien (William Fichtner) and is chambered in .338 Lapua Magnum. He later uses it while on the run. In reality, the rifle seen is a D&L MR-30 PG. The "Black King" is seen used by Swagger, O'Brien, as well as Lon Scott (Desmond Harrington).
Savage 110 (Saber-Forstt SVL-A2 MRC)
A Savage 110 action that is housed in a Saber-Forstt SVL-A2 MOD-1 Modular Rifle Chassis by Ashbury Precision Ordnance is the rifle given to Bob Lee when intially investigating the possible assassination attempt. The rifle is fitted with a suppressor and Schmidt & Bender PM II 5-25x56 scope on a 30 MOA rail. Swagger describes the rifle to National Security Adviser Gregson (Beverly D'Angelo) as a "Saber-Forstt .338 Precision Tactical Rifle" in Season 1's finale "Primer Contact" (S1E10).
Barrett Model 98 Bravo
The Barrett Model 98 Bravo is used by Swagger while in the Tree of Liberty camp in "Recon by Fire" (S01E05).
A Izhmash SV-98 rifle is used by an SVR Spetsnaz operator in "Primer Contact" (S1E10).
Knight's Armament SR-25
Swagger carries a camouflage-painted Knight's Armament SR-25 while in Afghanistan and as his personal hunting weapon in "Point of Impact" (S1E01). Special Agent Nadine Memphis also is seen training with a similar rifle. Some of the hired mercenaries use them in "Killing Zone" (S1E06).
M110 SASS
In what is apparently a continuity error, Swagger's SR-25 turns into an M110 SASS in "Point of Impact" (S1E01).
M40A5
Swagger's former mentor, Rathford O'Brien (William Fichtner), is armed with an M40A5 rifle while sneaking up in "Killing Zone" (S1E06).
Mk 12 Mod 0 Special Purpose Rifle
Memphis uses a Mk 12 Mod 0 SPR for sniper training in "Red on Red" (S1E08). She and Isaac arm themselves with Mk 12 Mod 0s to back up Swagger in the middle of "Primer Contact" (S1E10).
A Nemesis Arms Vanquish is seen in Swagger's shed in a flashback sequence in "Primer Contact" (S1E10).
Remington 700 BDL
In the series premiere "Point of Impact" (S1E01), a camo-painted Remington 700 is carried by one of the hunters that Swagger confronts. Swagger refers to the rifle as being chambered in .223 Remington. Swagger himself uses a 700 BDL in "Musa Qala" (S1E03). He also takes one from O'Brien's arsenal in "Killing Zone" (S1E06).
Remington 700 AICS
A Remington 700 AICS is used by a Tree of Liberty militiaman in "Recon by Fire" (S1E05).
Ruger M77 Gunsite
A Ruger M77 rifle is seen in a gunshow booth in "Danger Close" (S1E07).
Springfield M1A
A Springfield M1A with a desert yellow finish and a riflescope is used by Swagger in "Recon by Fire" (S1E05) when the ATF launches an anti-militia raid. One with a JAE-100 stock system mounted is seen is seen in Swagger's shed in a flashback sequence in "Primer Contact" (S1E10).
SVD Dragunov
A SVD Dragunov is seen in Swagger's shed in a flashback sequence in "Primer Contact" (S1E10).
Ruger M77
The Ruger M77 is used by militiaman Joey Richards (Alex Saxon) during target practice in "Recon by Fire" (S1E05).
Pistols
Beretta 92FS
While at the cabin, Swagger takes a Beretta 92FS from some old gear in "Musa Qala" (S1E03). It's also used as Swagger's sidearm during his time with the US Marines. He later pulls the Beretta during several confrontations.
Beretta 92FS Inox
A hunter who confronts Swagger pulls out a Beretta 92FS Inox in the series premiere "Point of Impact" (S1E01).
Colt Mark IV Series 80
A Colt Mark IV Series 80 is handed to Swagger when entering the TOL compound in "Recon by Fire" (S1E05).
Glock 17
Some law enforcement officers are armed with the Glock 17, including FBI Special Agent Nadine Memphis (Cynthia Addai-Robinson). Swagger briefly takes it from Memphis when he goes to her residence with one rigged up in a trap in "Musa Qala" (S1E03). Richards has one, but never fires it in "Recon by Fire" (S1E05). Some of the mercenaries in "Killing Zone" (S1E06) have them holstered.
Glock 19
Swagger takes what is most likely a Glock 19 off a guard and uses it to threaten Lon Scott (Desmond Harrington) in "Balllistic Advantage" (S1E09). During a confrontation, Julie can be seen with a Glock in Season 1's finale "Primer Contact" (S1E10) with Isaac packing it during a meeting with Gregson in a secret location.
Glock 34
Jack Payne (Eddie McClintock) pulls what appears to be a Glock 34 while masquerading as a Seattle police officer in "Point of Impact" (S1E01).
SIG-Sauer P226
An older SIG-Sauer P226 appears to be Jack's sidearm while with the DHS. Secret Service agent and ex-MARSOC officer Isaac Johnson (Omar Epps) tests the pistol in "Exfil" (S1E02). Isaac uses one with a suppressor in "Red on Red" (S1E08).
Both Swagger and Johnson are armed with the Heckler & Koch MP5SD3 during an infiltration in "Ballistic Advantage" (S1E09).
Assault Rifles
AKM
The AKM is seen with Taliban fighters in Afghanistan. Additionally, in "Primer Contact" (S1E10), an SVR Spetsnaz operator is armed with a custom AKM intended to stand in for the 2012 prototype of the AK-12; it has a Magpul Zhukov-S folding stock, Magpul PMAG, Tapco Intrafuse handguard, a railed top cover and an AK-12 style muzzle brake. This weapon was later used in the film Escape Plan 2: Hades.
AKMSU
The AKMSU is seen with Taliban fighters in Afghanistan.
AKS-74U
An AKS-74U is used by Isaac back in Afghanistan after a meeting goes wrong in Musa Qala in "Overwatch" (S1E04).
Colt M4A1
There are several appearances of M4A1s in the series. An M4A1 fitted with an CM203 launcher is carried by Donny Fenn (Rob Brown) during his tour in Afghanistan. An M4A1 is carried by several members of the Tree of Liberty militia, including Joey Richards. Isaac Johnson is armed with the M4A1 during a flashback in "Musa Qala" (S1E04).
Heckler & Koch HK416
The Heckler & Koch HK416 is used by the FBI's SWAT team as one of their main weapons.
Mk 18 Mod 0
One of Lon's men in "Ballistic Advantage" (S1E09) has what appears to be a Mk 18 Mod 0 with an Aimpoint sight, Magpul MOE handguard, and vertical foregrip.
Daniel Defense DDM4 MK18
A member of the Anhur Dynamics team is armed with what appears to be a suppressed Daniel Defense DDM4 MK18 rifle in "Killing Zone" (S1E06). In the same episode, Swagger uses the rifle until it jams. Isaac Johnson is seen in a vehicle armed with what appears to be an Daniel Defense DDM4 MK18 rifle fitted with a scope and bipod in "Red on Red" (S1E08). He later uses a different DDM4 as a short-range sniper rifle during a fight with a rogue SVR Spetsnaz unit in "Primer Contact" (S1E10).
Battle Rifles
M1 Garand
An M1 Garand is seen in the cabin and is used by Isaac during a sniper duel with Swagger near the end of "Musa Qala" (S1E03).
A Browning Auto-5 is seen on a sign in a Montana gun show in "Danger Close" (S1E07).
Mossberg 500 Cruiser
A Mossberg 500 Cruiser with a heatshield is seen in the hands of Leo, a convenience store operator, before Swagger disarms him of the shotgun in "Musa Qala" (S1E03). Swagger correctly identifies the shotgun as a "Mossberg 12 gauge" and mentions that the pistol grip sacrifices control and that it would likely kill both him and his hostage.
Remington 870 Express
In "Ballistic Advantage" (S1E09), Jack Payne (Eddie McClintock) can be seen with what appears to be a Remington 870 Express that he has taped to his hand and is using to hold Julie Swagger (Shantel VanSanten) hostage. This shotgun also is used by Julie.
Remington 870
In Season 1's finale "Primer Contact" (S1E10), Grigory Krukov (Sean Cameron Michael) is seen armed with Remington 870 12 gauge pump-action shotgun with a mounted saddle shell holder.
Machine Guns
Browning M2
A Browning M2 is seen mounted on US military vehicles, usually on Humvees.
Launchers
Cobray CM203
A short-barreled Cobray CM203 is seen on Donny's M4A1, standing in for the real M203 grenade launcher, in a picture of him, Swagger, and Isaac in Afghanistan near the end of "Exfil" (S1E02). It is seen again on Donny's M4 in "Overwatch" (S1E04).
RPG-7
The RPG-7 is used by a Taliban fighter in Afghanistan in "Overwatch" (S1E04).
In the series premiere "Point of Impact" (S1E01), Swagger is seen keeping several sniper rifles and sidearms in his cabin. Another shot of his cabin is seen at the end of "Primer Contact" (S1E10).
Gun Store
A gun store is visited by Swagger in "Point of Impact" (S1E01).
Montana Gun Show
Several small arms are seen on display in a Montana Gun Show in the middle of "Danger Close" (S1E07).
Lon Scott Arsenal
In his residence, Lon Scott keeps a variety of rifles mounted on a wall.