The Kimber Warrior was the sidearm of choice for Jonas Blane throughout Season 4 (and occasionally in earlier seasons), replacing the Custom TLE II.
Colt M1911A1
The M1911A1 is a frequent weapon seen in the series. Master Sgt. Mack Gerhardt (Max Martini) carries one as his sidearm. An M1911A1 with a suppressor and night vision scope was used by Bob in Season 4's "Dancing Lessons". Another scoped 1911 (likely the same prop weapon) was used by one of the terrorists who tries to kill Jonas when he rescues Molly in "Endgame".
SIG-Sauer P225
The SIG-Sauer P225 is used by Sgt. Charles Grey (Michael Irby) with a suppressor in Season 4's "The Last Nazi" (S4E14). SSgt. Sam McBride (Wes Chatham) is seen with a P225 in the opening scene of Season 4's "Hero".
SIG-Sauer P226
The SIG-Sauer P226 is the sidearm of Sgt. Charles Grey (Michael Irby) and Sgt. Hector Williams (Demore Barnes) throughout the series. Master Sgt. Mack Gerhardt (Max Martini) uses a P226 throughout Season 1 before switching to his M1911A1. P226s are used by a number of Leon Drake's men (including Drake himself) with and without suppressors throughout Season 4.
SIG-Sauer P229
The SIG-Sauer P229 is a commonly featured handgun throughout the series. US Army intelligence officer Bridget Sullivan (Nicole Steinwedell) uses a two-tone P229 in the Season 4 premiere "Sacrifice" (S4E01). Mack mentions that she carries a .45, which is incorrect, as the P229 is only chambered in 9mm, .40S&W, and .357 SIG). Bridget's P229 is briefly seen again in "Best Laid Plans". Similar weapons (likely the same prop guns) are used by the female kidnapper in "Dancing Lessons", and the assassin in "The Last Nazi".
SIG-Sauer P230
A suppressed SIG-Sauer P230 was used by one of the Russians who ambushes Bob in Season 4's "Endgame".
Glock 17
The Glock 17 is one of the weapons prominently featured throughout the series. Charles Grey (Michael Irby) uses a Glock 17 during the opening scene of "Sacrifice".
Glock 19
The Glock 19 is also used by numerous characters throughout Season 4. President-elect Benjamin Castillo (Benito Martinez) is seen with a Glock when he is confronted by the team in Season 4's "Sacrifice". They are used frequently by terrorists in other episodes, including "Switchblade", "Inquisition", and "Dancing Lessons".
Glock 26
A Glock 26 is briefly seen among other handguns when Sam (Wes Chatham) is choosing his sidearm. He initially selects the G26 but is convinced otherwise by Mack and takes a USP .45 instead.
Beretta 92FS
The Beretta 92FS has been seen in the hands of SWAT members, Unit members, and US military CID agents. Sam McBride (Wes Chatham) takes a 92FS from a police officer in "Whiplash" (S4E19).
In "Sex Trade" (S4E03), Bridget takes a Heckler & Koch P7 off a dead terrorist.
Cobra Big Bore Derringer
In Season 4's premiere "Sacrifice" (S4E01), Army intelligence officer Bridget Sullivan (Nicole Steinwedell) carries a chrome plated Cobra Big Bore Derringer as a backup that she has to use when engaging a terrorist disguised as a National Guardsman.
Norinco Model 54
Norinco Model 54 pistols were used by Chinese officers in Season 4.
Kahr K9 M9098 Elite
In Season 4's "Sudden Flight" (S4E2), the head terrorist uses a Kahr K9.
Makarov PM
The team finds a Makarov PM on a deceased Spetznaz member in Season 4's "Chaos Theory", and identified by Bob as "Kirovsky(?) 9mm armor-piercing Standard Spetznaz Issue". In all likelihood, this is meant to stand in for an SR-1 Gyurza, though it is clearly a Makarov, with the grips being the most obvious giveaway. There is a noticeable goof when the team finds the weapon: in the initial shot of the stairway the Makarov is gone, it only appears during the close up shot. Other Makarovs are seen throughout the episode. O
Smith & Wesson 6904
A Smith & Wesson 6904 is among the handguns seen in the gun drawer when Sam selects his sidearm in Season 4's "Hero".
Smith & Wesson SW99
In Season 4's "Best Laid Plans", one of the men employed by Leon Drake (David Rees Snell) tries to use his S&W Model 99, but it doesn't fire.
Jericho 941 R
In Season 4's "Flesh & Blood", Joss' bodyguard carries a reverse two-tone Jericho 941 R, which he expertly relieved of by Grey.
Revolvers
Colt New Service
A Colt New Service is seen when Jonas searches Sam's storage unit in Season 4's "Whiplash".
Webley Mk IV
A Webley Mk IV is seen in the hands of a tribal member is Season 4's "Shadow Riders"
Smith & Wesson Model 36
In Season 4's "Sex Trade", a Smith & Wesson Model 36 is planted on a male student who tried to blackmail Tiffy.
Smith & Wesson Model 60
A Smith & Wesson Model 60 was seen in the Season 4 premiere "Sacrifice" as Mack's throw away gun.
Colt Single Action Army
In Season 4's "Switchblade", Grey is seen restoring a classic Single Action Army.
Submachine Guns
Heckler & Koch MP5A3
In Season 4's "The Last Nazi", a bodyguard carries a Heckler & Koch MP5A3 equipped with a tri-rail, Aimpoint red dot sight, and vertical foregrip.
Heckler & Koch MP5SD3
Heckler & Koch MP5SD3s are seen used by the Unit in several episodes including Season 2's "Dark of the Moon" and "Report By Exception", and the Season 4 premier "Sacrifice". Strangely, in season 4, the sound effects used are those of unsuppressed weapons.
Jonas, Mack and Hector are all seen using Heckler & Koch MP5K submachine guns in the series. Jonas and Mack were seen using the newer Navy trigger group variant, while Hector was seen using one with the old "SEF" trigger. Bob also uses one in Guyana to cover Jonas's escape. In Season 2's "Sub-Conscious", Kim Brown (Audrey Marie Anderson) is also seen using one in a dream sequence.
Heckler & Koch MP7A1 PDW
In Season 3's premiere "Pandemonium, Part 1", an assassin goes after Jonas and CIA operative Mariana Ribera (Tia Texada) with a Heckler & Koch MP7A1. The weapon is also used in season 4 episode 15.
Heckler & Koch UMP45
A Mexican Special Forces member is briefly seen holding a Heckler & Koch UMP when taking orders from Mack in Season 4's "Sudden Flight".
Sten
A Sten is fired by guards in the Season 2 finale "Paradise Lost".
Uzi
A full size Uzi was featured in several episodes. Grey was also seen with one in season 4.
Mini Uzi
A Mini-Uzi is used by a hijacker on the plane in Season 1's premiere "First Responders". Bob also uses one in Season 4's "The Conduit" (S4E4).
Micro Uzi
A Micro-Uzi is used by a terrorist in the series finale "Unknown Soldier".
MAC-10
The MAC-10 is seen in the hands of Mexican smugglers in Season 2's "Manhunt".
Cobray M11/9
Dragovich (Yasen Peyankov) uses a Cobray M11 in his attack on the Unit during the Col. Ryan's reception dinner in the Season 1 finale "The Wall" (S1E13).
Beretta PM12S
Hector smuggles a Beretta PM12S into a diamond mine in Season 2's "Old Home Week" (S2E6) and is used by both Jonas and Hector. Jonas and Grey uses them in their escape in Season 4's "The Conduit" (S4E4).
Steyr SPP
Hector also smuggles a Steyr SPP into a diamond mine to be used by Bob in Season 2's "Old Home Week". The SPP is the civilian verison of the TMP modified for full auto.
Škorpion vz. 61
Seen used by terrorists in Season 3's "Inside Out" (S3E5) and hijackers in Season 4's "Sudden Flight" (S4E2). One was also seen in the hands of an Iranian embassy guard in the Season 1 episode "Security."
AP-9
One of Dragovich's men uses an AP-9 in the attack on the Unit during the reception dinner in Season 1's "The Wall".
Hotchkiss "Type Universal"
A Hotchkiss "Type Universal" is briefly seen in Season 2's "The Broom Cupboard" (S2E12). While the Hotchkiss is a French weapon, it's implied that the US government is supplying the rebels with them.
MAT-49
At least one of the Indonesian rebels carries a MAT-49 in Season 1's "200th Hour".
Assault Rifles
Colt M4A1 Carbine
M4A1 Carbines are used by all members of the Unit, often with a 40mm M203 Grenade Launcher, and with an optical sight (normally the Trijicon ACOG, Aimpoint CompM2 and/or EOTech 552 Holographic sight). Sometimes they switch with HK 416s.
Special
M16A1
While M16A2's are more prevalent in the series, the M16A1 is also featured in several episodes.
M16A2
M16A2 rifles are seen usually in the hands of non Unit members of the military such as regular Army units in Season 2's "Dark of the Moon". In Season 3's "Play 16", Mack was seen cleaning and preparing Hector's M16, including attaching an M9 bayonet (though strangely, an M4 is used at his funeral instead).
Special
M16A4
In Season 2's "Dark of the Moon", at least one US Army soldier can be seen armed with an M16A4 rifle, identified by the removable carry handle/rear sight assembly.
Special
Custom M16
In Season 2's "Natural Selection", Bob uses an unusual variant of the M16 during his Unit selection training. It appears to be neither an A1 or A2, as it has an upper receiver with A1 sights and the heavier-profile A2 barrel with A2 handguards. Most resembles a Model 715 (Canadian C7), but until a better shot of the right side of the receiver comes along or the episode's armorer himself states, a definite ID is impossible.
Heckler & Koch HK416
One of the rifles that Unit members use is the Heckler & Koch HK416 in the the D10RS sub-variant with a 10 inch barrel. Grey and Jonas both use 416s with ACOG scopes mounted on M4 carrying handles in the Season 2 Finale "Paradise Lost", the others usually have the EOTech 552 Holographic sight attached (in Season 3's "Every Step You Take" (S3E04), Bob's EOTech disappears and reappears a few times). Mac uses one in Season 3's "Inside Out" (S3E05). Colonel Ryan uses one in Season 4's "Into Hell Part 1", though it is very difficult to identify clearly (the DVD extras provide a better view, albeit briefly).
Colt Model 933
Colt Model 933s were used by Jonas, Mack, Bob, and Grey in the Season 3 episodes "Five Brothers" (S3E7) and "Play 16" (S3E8), but note that in the latter episode they switch to HK416s a couple times in a continuity error, which implies they are intended to stand in for them. They are seen outfitted with EOTech 551 Holographic sights, AN/PEQ-2s, Crane stocks, vertical foregrips, and rail mounted flip-up front sights, but strangely lack a rear sight, although one shows up on Jonas's rifle sometimes in another continuity error.
Mark 18 Mod 0
Grey wields a custom built Mark 18 Mod 0 rifle in the opening scene of Season 4's "Hero". It appears to be the same weapon used by Jack Bauer in Season 7 of 24. Despite being equipped with a red dot sight and magnifier, the reticle shown is that of a normal rifle scope.
Heckler & Koch G36C
The Heckler & Koch G36C is carried by Sgt. Grey in the Season 1 finale "The Wall".
SIG SG 552
Sgt. Grey carries a SIG SG 552 in Season 1's "Stress" (S1E02). Jonas, Bob, and Hector all carry these rifles in the Season 1 finale "The Wall" (Jonas's is briefly seen with a suppressor).
FN FAL
Several FN FAL Variants are seen in the hands of Jonas and Hector in episode 2 of season 1. Jonas uses one with iron sights while Hector's is fitted with a scope. These were the full length FALs and one might of had a wooden stock. It was hard to tell. In season 3, episode 4, there was a couple FALs used by the enemy.
SA Vz.58
In Season 2's "Bait", the Georgian rebels who hold Jonas hostage are armed with SA Vz.58 rifles.
AK variants
Variants of the AK are featured throughout the series. All members of the Unit is seen using an AK at least once throughout the series. Most enemies have also used the rifle.
M70B1 and M70B2
AKMSU
The shorty AKMSU carbines (AKM rifles converted with Krinkov parts kits and AKS-74U side-folding stocks) were used in several episodes.
Seen throughout the series, but featured prominently in Season 2's "Johnny B. Good", where each member of the Unit carries an AKM rifle fitted with suppressor and Surefire light on their mission to Iran.
Special
FN F2000 Tactical
Jonas can be seen using an FN F2000 Tactical fitted with a scope in Season 2's "Extreme Rendition" (S2E2).
FAMAS
The FAMAS rifle is seen in the hands of French Soldiers in Season 1's finale. Also seen in the hands of soldiers in South East Asia.
Ruger Mini-14
A Ruger Mini-14 is seen resting on a tree by one of the terrorist lookouts that Bob takes out in Season 1's "First Responders". Also seen used by a man in episode 4 of season 1.
Heckler & Koch G3
Heckler & Koch G3 rifles are used by rebel forces aiding the Unit in Season 4's "Flesh & Blood" (S4E17).
Heckler & Koch HK91
A Heckler & Koch HK91 is used by a boy soldier used by an arms dealer to guard his home in Season 1's "Eating the Young" (S1E9). Some are obviously non-firing replicas, likely done for the safety of the child actors.
Galil ARM
One of the guards fires at the Unit with a Galil ARM in Season 4's "The Conduit".
Shotguns
Mossberg 500 Cruiser
A Mossberg 500 Cruiser is seen among the weapons packed on a mule in Season 1's "First Responders" (S1E1).
Benelli M3 Super 90
The Benelli M3 Super 90 shotgun are the main weapons of Alpha Team members Charles Grey (Michael Irby) and Hector Williams (Demore Barnes) in the Season 1 premiere "First Responders". Also seen in the hands of the US Rangers that accompany them in the assault of the plane.
Stevens 512 Gold Wing O/U Shotgun
Jonas shoots skeet with a Stevens 512 Gold Wing O/U Shotgun chambered in 12 gauge owned by the Oil Minister. (It seems that even high-ranking government officials cheap out on shotgun choice.)
Sawed off Double Barrel
In Season 2's "Manhunt", Jonas finds a sawed off double barrel shotgun from behind the counter of a white supremacist's hardware store.
Remington 870 Wingmaster
Mack used a vintage Remington 870 shotgun while posing as a bird hunter in episode 4 of season 1.
Ithaca 37
The Ithaca 37 shotgun is carried by a harbor guard in Season 3's "Pandemonium, Part 2" (S3E2).
Machine Guns
FN MAG mocked up as M240
FN MAG machine guns mocked up to resemble the M240 are seen in use by French UN forces in the Season 1 finale "The Wall" and by US Army troops in Season 2's "Dark of the Moon". They are recognizable as the M240G due to lack of heat shield but most likely, these are actually original FN MAGs mocked up to look like the M240G. In Season 3's "M.P.'s", Mack is seen firing one fitted with the heat shield and synthetic buttstock.
Special
FN Minimi (M249 Para)
Hector (Demore Barnes) is seen with an FN Minimi mocked up to resemble the M249 Para in his final mission in Season 3's "Five Brothers".
Browning M2
A Browning M2 HB is taken over by Hector in Season 2's premiere "Change of Station". The M2 also is prominently seen mounted on top of humvees driven by regular Army in Season 2's "Dark of the Moon".
Browning M2 Aircraft
A Browning M2 Aircraft model is seen used as a doorgun on the UH-1 Huey sent to extract the Unit in Season 4's "Into Hell, Part 2" and again in "The Spear of Destiny".
PKM Machine Gun
A PKM Machine Gun was used by African forces in Season 1's "Stress" (S1E2).
RPK
An RPK light machine gun was used by a terrorist in Season 3's "Always Kiss Them Goodbye" (S3E3) during the shootout in the aircraft hangar.
RPD
In Season 4's "Into Hell, Part I", one of the sentries that confront the Unit at the Syrian border is seen handling an RPD machine gun.
M60
An M60 machine gun is seen in the arms cache found by Bob Brown and Dr. Donald Metz (Michael McKean) in Season 4's "Switchblade".
M60E4/Mk.43 mod. 1
An M60E4/Mk.43 mod. 1 MG was used by Jonas briefly in Season 4's "Into Hell, Part I" (S4E7). The E4's distinctive picatinny rails on the receiver cover and forend, and the removable front grip are visible on Jonas' weapon.
Browning Automatic Rifle (BAR)
In Season 2's "Silver Star", a US Army soldier is briefly seen using a Browning Automatic Rifle during the Korean War flashback.
DShKM Heavy Machine Gun (Browning M2 mockup)
A Browning M2 mocked up to resemble the DShK heavy machine gun is frequently used in the series. It's fired by Taliban warriors in Season 1's "Dedication" (S1E7), set up by Syrian forces in Season 4's "Into Hell, Part II" and fired by Mack in Season 4's "Switchblade".
Sniper Rifles
Mark 12 Mod 0 SPR
A Mark 12 SPR is used by Jonas in "Eating the Young" (S1E9).
M16A4 (Sporter Competition H-Bar)
M16A4s were shown prominently in Season 2's "The Kill Zone" (S2E3) where for some strange reason, the entire unit went into the field carrying them and their man that was pinned down was also carrying one. It was noted that Jonas recognized the sound of a "7.62" shot distinctly over the enemy sniper's weapon to recognize it as one of their own (hinting that these are supposed to be standing in for SR-25 rifles. The fact that they use 20 round magazines futher supports this theory). The problem is that all of their rifles fires 5.56 including the man they were rescuing, who clearly was using an M4. At the beginning of the episode Bob was training a group of Unit recruits who were all using these rifles. Propwise, these are probably the same ones used later in the episodes by the rest of the Unit cast out in the field. While they are usually seen fired in semi auto mode, Mack fires a burst of 5-10 rounds proving that these rifles are in fact capable of full auto fire.
It's worth noting that the sound signature of the "7.62" that Jonas recognized was much beefier than that of a 5.56.
Armalite AR-10
In Season 1's "Dedication", Bob uses an Armalite AR-10 was dressed up as a sniper rifle, most likely as a placeholder for the Knight's Armament SR-25. It is not a SR-25 due to the the fencing around the magazine release, the SR-25 lacking this feature. Bob fires it on full auto while in the chopper, despite the fact that its trigger group clearly lacks an "Auto" option, but this was most likely added in post-production editing because no casings are ejected and the dust cover remains in place.
Cheyenne Tactical M-200 Intervention
Two Cheyenne Tactical M-200 Interventions were used by Bob Brown and Hector Williams in the Season 2 episode "Dark of the Moon" to engage the enemy targets.
Note: on the DVD commentary for S3E1 "Pandemonium Part 1" theses rifles are misidentified by cast and crew members as ".50 caliber sniper rifles."
Special
Heckler & Koch PSG1
Mack used a PSG1 in "Stress" (S1E2) with great effect. His rifle had a 20 round magazine in it.
Remington 700 AICS
A sniper rifle frequently used by The Unit is a Remington 700 AICS. Bob is seen firing one in Season 1's "Non-permissive Environment". Mack also used this in Season 4's premiere "Sacrifice" and again in "Endgame". Sam McBride (Wes Chatham) is seen with this rifle in Season 4's "Best Laid Plans" (fitted with a Elcan Digital Day/Night scope, which is inaccurately portrayed not only as being a thermal scope, but as being able to detect heat through windows and curtains) and again in "Whiplash". The action is a Remington variant since the bolt is not an AI design. The folding stock hinge and adjustable cheek piece are visible in the close-up, so this would be an AICS 2.0 model. Also, AI L115 rifles are generally outfitted with Schmidt and Bender PMII scopes which this scope is definitely not. Also, unless the magazine has been removed (unlikely during a mission), the magazine on an actual Accuracy International AW/M will be protruding from the bottom of the stock. You can clearly see the paddle style magazine release in front of the trigger guard which would normally be blocked by an inserted magazine. This rifle is the same rifle used by Micheal Weston in season 2 of Burn Notice. The giveaway is the scope rings are the same cheapies seen on Jonas' rifle here. They should be heavy badgers or warnes.
Remington 700PSS
Mack Gerhardt (Max Martini) wields a Remington Model 700PSS rifle chambered in either .308 or .300 Winchester Magnum in Season 3. This scene is also prominently featured in the Season 4 opening.
In Season 3's "Gone Missing" (S3E10), the Unit goes on a mission armed with the Blaser R93 LRS2 Precision Sniper Rifle as their sniper rifles. In the episode, the Blaser used a new type of ammo filled with mercury that was designed specifically not to over penetrate. The rifles were handled by Bob, Grey and Mack with Jonas alternating with Bob a couple times. The sound effect used is that of a suppressed round when clearly none of the rifles were suppressed. Another of these rifles was used by an enemy sniper in Season 4's "Flesh & Blood".
AIG Asymmetric Warrior ASW338LM
In Season 4's "Best Laid Plans", Bob Brown (Scott Foley) is seen with a Gen 2 AIG Asymmetric Warrior ASW338LM modular sniper rifle in .338 Lapua Magnum while covering Jonas and Mack. Bob uses this rifle again during the standoff with Sam in "Whiplash".
Rifles
Lee-Enfield No.1 Mk.III
A Taliban warrior uses a Lee-Enfield No.1 Mk.III to wound a chopper pilot in Season 1's "Dedication" (S1E7). In Season 2's "Dark of the Moon" (S2E17), many tribal warrior use Enfields as they attack the Unit and the American forces.
Special
SKS rifle
The SKS rifle was used by terrorists in Season 2's "In Loco Parentis" (S2E20). The rifle was also seen in Season 1's "200th Hour" (S1E3).
Special
M1 Garand
In Season 2's "Silver Star", the M1 Garand rifle is seen used by US forces, including Jonas' father during the Korean War flashback.
M1 Carbine
In Season 1's "200th Hour" (S1E3), Indonesian rebels are seen carrying M1 Carbine rifles.
Marlin Model 336
The Park Ranger who gets shot in the Season 4 premiere "Sacrifice" is seen with a Marlin Model 336. Bridget is seen putting the rifle on the Ranger to distract the terrorist shooting at her. Another is seen in Carson's truck in "Switchblade."
Kentucky Flintlock Rifle
In Season 4's premiere "Sacrifice", Grey finds a Kentucky Flintlock Rifle in the cabin when they prepare to make their last stand. They don't fire it, but they use the black powder to make an improvised explosive.
Hi-Point Carbine
One of the terrorists who attacks the wedding reception in Season 1's "The Wall" uses a Hi-Point Carbine. Despite being a semi auto weapon in reality, it is depicted firing full auto. Obviously that terrorist had converted that weapon into full auto.
Heavy Weapons
M203 Grenade Launcher
An M203 Grenade Launcher is seen mounted underneath Jonas' M4 in "Exposure" and Mack's in "Dedication". Hector is also seen leading a group of US Army soldiers with M203's in "Dark of the Moon".
Cobray CM203 37mm Flare Launcher
M4A1 carbines fitted with the Cobray CM203 37mm Flare Launcher standing in for the M203 were used by Bob, Grey, and Mack on the mission to Iraq to rescue Betsy Blane in Season 4's "Into Hell: Part 1" (S4E7) and "Into Hell: Part 2" (S4E8).
FIM-92A Stinger
Bob Brown (Scott Foley) is seen taking out a helicopter with a FIM-92A Stinger in the Season 1's "Eating The Young."
Chinese Type 69 RPG
Several Type 69 RPG's are seen being used throughout the series. In Season 1's "The Wall", Dragovich's men fire one at oncoming French forces. In Season 2's "Dark of the Moon", Jonas takes one from a fallen tribal warrior and uses it on the onslaught of the enemy. Both examples seen here are the Chinese Type 69 launcher (the Chinese version of the SovietRPG-7). The biggest difference is that the Chinese RPG had only one pistol grip. The second hand has to grasp a carry handle on top of the launcher. The Type 69s in the series have PGO-7 scopes mounted on the launcher.
Special
Other Weapons
M67 "Baseball" Grenade
The M67 "Baseball" Grenade is used throughout the series. Bob uses one to spike a mortar in Season 1's "Dedication". He also uses one in Season 3's "Every Step You Take". In Season 4's "Whiplash", Sam booby traps the door to the office he barricades himself in with three M67s.
M26 "Lemon" Grenade
A terrorist attempts to use an M26 hand grenade in Season 4's "Hill 60" before being shot. Jonas finds a crate of them in Sam's storage locker. Sam later uses one to aid his escape, though strangely when he barricades himself in the auto dealership office, he is shown to have booby trapped the door with M67 grenades.
CTS Model 7290M Mini Bang
A CTS "Mini Bang" is used by Jonas (combined with some drugs and chemicals found in the lab) in Season 4's "Mislead and Misguided." During the standoff in "Whiplash", Sam holds one up to the window, calling it a concussion grenade. It should be noted that, though flashbangs are often erroneously called concussion grenades, the two are very different, as concussion grenades are much more deadly then flashbangs. Given the dialog of the scene, it's likely that the filmmakers intended for this to be an actual concussion grenade, and simply used a prop flashbang during filming.
"ALS" prop Flashbang
Sam McBride uses an unknown Flashbang in the opening scene of Season 4's "Hero". Jonas can be briefly seen with a pair of these strapped to his vest in Season 3's "Play 16." They bear the logo of ALS Technologies (a real company which actually makes stun grenades), however they look nothing like any product in ALS's catalog. These are likely prop replicas.
Unknown Grenades
Seen briefly in the series premier "First Responders" among other weapons are two different grenades of unknown type.
Crossman Air Pistol
Two Crossman air pistols loaded with tranquilizers were used by Afghan Tribesmen to incapacitate Jonas and Mack in Season 4's "Shadow Riders."
Wheelie bag carrying handle gun
In Season 4's "The Conduit" (S4E4), Bob and Jonas had these weapons disguised as the carrying handles for their wheelie bags. It appears each of the square extendable rods were hidden barrels that each load one round, possible .22 or something small. To fire, they collapse the carrying handle forward into the smaller rod like you would a carrying handle of this type and it fires both rounds at the same time. I don't know if this is a real firearm, but it acts like one. Meant to be used to disarm armed men with real guns.
Gun Racks
When Grey is taken to Carson's house in Season 4's "Switchblade," a gun rack with unknown rifles on it is seen briefly. Two others are seen in the hardware store in Season 2's "Manhunt."