The following weapons were used in the film Jurassic Park:
A Franchi SPAS-12 is used by Robert Muldoon (Bob Peck) and Dr. Alan Grant (Sam Neill) over the course of the movie, also seen in the hands of several InGen workers in the introduction and in the gun lockers. It is last seen lying discarded on the computer room floor after jamming due to a stovepipe malfunction when Grant used it to try to fend off an attacking Velociraptor.
Franchi SPAS-12 - 12 Gauge
Muldoon oversees the loading of a Velociraptor
armed with a SPAS-12 shotgun.
Muldoon folds the stock open on his SPAS-12 shotgun.
Muldoon folds open the butt on his SPAS-12 shotgun.
Muldoon takes aim at a Velociraptor
with his SPAS-12, only to realize he has been tricked. Note how he doesn't actually have the stock pressed into his shoulder but barely rested against his bicep; the weapon would likely slip under his arm if he pulled the trigger now.
Grant pumps the action on a SPAS-12 shotgun.
Grant throws down the SPAS 12 after it jams. The jam appears to be an extractor malfunction, resulting in a shell in the breach holding back a loaded round from being chambered, commonly known as a 'stovepipe'. Such a jam is relatively straightforward to clear in reality, but given that Grant is merely a paleontologist, it makes sense that his character might not be familiar enough with firearms to know how to do so. The shells used in this scene are most likely dummy rounds given how fragile they appear.
The M16A2 is seen carried by several InGen workers in the beginning of the film and is stored in the gun lockers in the emergency bunker. Most of the M16A2's carried by the workers can be seen fitted with weaponlights mounted on the barrels ahead of the front sights.
On of the InGen workers next to Muldoon armed with an M16A2.
An InGen worker armed with an M16A2.
M16A2 rifles seen in the gun locker as Muldoon grabs a SPAS 12.
Some of the Ingen workers are also seen with 'slab-side' M16 rifles, or possible AR-15/SP1s. Then again, they could be simple rubber props modeled after said rifles. They are fitted with A2-style handguards to pass for an M16A2.
M16 aka SP1 (flat "slab side receiver") with A2 style handguards used to impersonate the M16A2 - 5.56x45mm
An InGen worker is seen armed with a slab-side M16 rifle when the Raptor looks out of its cage.