XM177-type carbines are the main weapons carried by LT Jordan O'Neill (Demi Moore) and the majority of the applicants in the SEAL CRT program. During the Libyan mission, the weapon is carried by Master Chief Urgayle (Viggo Mortensen) and other members of the team. The XM177s in the movie all have M16A2 or Model 715-style receivers, while the real XM177 variants only had M16A1 or SP1-type receivers. Rifles similar to these have appeared in many other movies and TV shows, such as The Rock and Seven Days. During the training, a weapons instructor describes the gun as a "CAR-15, military designation M4", but the guns shown in the movie are quite clearly not M4s.
M16A2
An M16A2 rifle is carried by Slovnik (Jim Caviezel) and several other SEALs.
M16A1 (with M16A2 hand guards)
M16A1 rifles fitted with M16A2 handguards were carried by the U.S. SEALs and US Army Rangers during the Libyan mission.
Norinco Type 56
The Norinco Type 56 is used by the Libyan forces that engage O'Neill and the team.
Submachine Guns
Heckler & Koch MP5SD3
The Heckler & Koch MP5SD3 is the chief weapon of Wickwire (Boyd Kestner) during the Libyan mission. The weapon is also seen carried by a US Army Ranger during the recovery mission.
Heckler & Koch MP5A3
One of the CRT applicants is seen armed with a Heckler & Koch MP5A3 before entering the SEAL obstacle course.
Heavy Weapons
M203 Grenade Launcher
An M203 Grenade Launcher is seen attached underneath O'Neill's XM177 during the Libyan mission as well as carried by the SEAL applicants during the obstacle course.
M60
An M60 general-purpose machine gun is seen being fired by instructors during the SEAL obstacle course.
M60E3
The M60E3 is seen being assembled by O'Neill and other members of her team during the SEAL training. It is also the chief weapon of Cortez (David Vadim) during the Libyan mission.
DShK heavy machine gun
A DShK is seen mounted on a Libyan truck that fires on the team. It's hard to tell, but this is most likely a mocked-up Browning M2 variant, like nearly all "DShK" HMGs seen in Western productions.
Browning M2HB Heavy Machine Gun
During the SERE training, a Browning M2HB heavy machine gun is seen mounted atop a Humvee in the encampment where Jordan and her team are taken prisoner.
Sniper Rifles
SVD Dragunov
Master Chief Urgayle (Viggo Mortensen) can be seen firing an SVD Dragunov sniper rifle during the obstacle course training.
Heckler & Koch SR9(T)
Master Chief Urgayle (Viggo Mortensen) uses a Heckler & Koch SR9(T) during the Libyan mission. The SR9(T) in this movie, like all SR9 rifles seen in American films, is actually a HK91 converted to SR9(T) specifications (note that it lacks the forward assist, which is a feature of the factory SR9 variants). While being chased by Libyan soldiers, he booby traps the weapon with a M67 grenade.
M1911A1
A Libyan soldier pulls an M1911A1 before being taken out by Urgayle. A US Navy helicopter crewman opens fire with an M1911A1 as Jordan and the team make their way to the helo.