Goofs

When Harry is buying the gun there is a girl lying on a the couch. When viewed from Harry's perspective her head is laying flat on the couch, in the shot from across the room her head is propped up against the arm of the couch.

During the riot scene, a Volvo hatchback is torched using a petrol bomb. Later in the sequence the car is seen again, and the fire has gone out. It is possible, although unlikely, that the petrol did not ignite the interior (accelerants in isolation do not burn for long), but the car body shows no oxidation or paint damage, even around the roof.

Harry reviews the street from Leonard's flat. We see a couple approach the dealers. She wears a back pack. Then she loses it. In the scuffle that follows, we do not see where her bag goes to.

At the canal, D.I. Frampton says to D.S. Hickock that she smelled cordite on Harry Brown's coat, implying him having fired a gun. Cordite is obsolete: it's no longer produced. This is a forgivable mistake though, because although cordite production ended in the 1960s, the term is still used generically in the UK for gun powders.

The large map behind SI Childs in his office when he's talking to DI Frampton is of Cheltenham, Gloucestershire. This is an odd priority for a senior police officer in London.

Although supposedly set in south London, most of the graffiti on the estate has been lifted straight from the New York underground scene by the movies art department, with internationally recognized American Graffiti artists such as 'Kez' and 'Skuf' and 'YKK crew' adorning the supposedly British sink estate.

The underpass in the movie is around 30 miles from Harry's house in south London where the movie is set. When Harry looks out of a broken window at the kids in the underpass you can see the road sign showing right for Dagenham left for Marks Gate. Additionally, there is no canal on either side or high rise buildings like Harry's home anywhere near so they used a different location for those shots.

The Filming Locations section tells us the canal is Regent's Canal, Islington. Creative geography is a widely used cinematic device.

Kenneth (Joe Gilgun) claims the SIG P226R pistol is made from polymer reinforced with fiberglass. This is incorrect as the P226R has a steel frame. However, the Glock 17 he offers for sale does have a polymer frame.