Is the gun used in 'Law Abiding Citizens' real?

Answer 1

According to imfdb, the weapons used in the movie included:

• Glock 17
• Heckler & Koch MP5A2
• M4A1 carbine (traditionally Colt, but for law enforcement, other companies have been awarded contracts to provide these weapons for SWAT teams)
• Browning M2HBAR
• Bofors Carl Gustav M134 (AT4)
• Cell Phone Gun

Of these, only the cell phone gun appears to be somewhat fictional - cell phone guns are real, but they are user activated, and serve as clandestine weapons, rather than firing when a call is received.

As for the weapons themselves used in the movies, the answer is probably yes and no, both. Movie sets use real firearms, fitted with blank barrels. However, as a cost saving measure, weapons not being shown firing in the movies are often "rubber duck" reproductions of weapons - they're non-functioning, made mostly of plastic, although they usually do have real barrels, as these were originally fashioned as a substitute to using real rifles in bayonet training.