When two groups are conflicting at first; In a few scenes, the shards of glass around the van's broken window disappear and reappear, and the light inside the van decreases and increases.

During a quiet moment in the shooting, Ord lights up a joint. While smoking it, he holds it in the "dart position" finger and thumb, as joint smokers do, and sometimes in the "cigarette position" between the first two fingers. At one point, the positions switch abruptly between frames.

Contrary to popular belief, a localized fire will not set off the entire sprinkler system and drench a whole building, since the water can only be released by shattering a heat-sensitive glass bulb located inside each individual sprinkler head.

Perhaps in residential, retail, public and office buildings. In industrial, especially older industrial settings and particularly if there are flammable liquids produce or stored there, the whole area needs to be flooded to contain any fire until the fire fighters arrive.

Vernon, the South African "child genius", believes that since he shot one of the snipers he's on the hook for the death penalty in Massachusetts. The last executions in Massachusetts were performed in 1947, and capital punishment was abolished there in 1951. Vernon is misinformed, which should surprise no one.

When Ord (Armie Hammer) tears the wires that interrupt Chris' (Cillian Murphy) phone call, the wires he tore are clearly not phone wires, not even 1970's DC system wires, but electrical wires. Phone systems and electrical service are on separate electrical systems, so tearing electrical wires from the wall would have no effect whatsoever on a phone system, then or now.

Even if they did, the wires he tears on the factory floor would not have any bearing on the phone service in the upstairs offices, just on extensions on the factory floor. That phone call would not have been cut off.

The pressurized bottle (color coded brown with white rings), that was shot and produced a rocketing tank with fire is Helium. Which does not burn.

The idea that Chris' own ammo, which he brought to use trying out the M-16's he ordered, wouldn't work in the SC-70's that Vernon delivered is false. Both rifles are chambered in the same 5.56x45mm NATO round, and also fire .223 Remington, so any such ammo Chris might have brought would work in either rifle.

After Harry drives his van into the deserted warehouse while playing plays John Denver's "Annie Song" in his cassette, he gets out of his van, stopping the music at the interlude. But, later, when injured Harry attempts to escape with his van, it resumes the song at the intro.

The filmmakers chose that moment to tie in Annie's Song with the background sound track. The song started before the tape was pushed in to play and can be heard with no change of volume as the camera pans around the other characters. The rest of the side of the album (Back Home Again) plays through the closing credits.

Chris complains that he ordered M16s and received AR70s. In fact the assault rifles delivered are the Beretta SC70, which is the rare folding stock version of the AR70. The AR70 and its derivatives are the standard-issue weapon of the Italian armed forces. The problem is that the film is set in 1978, but the AR70 wasn't developed by Beretta until the 1980s.

Edit: The AR70/90 was developed in the '80s, the AR 70 A was developed in the '60s and '70s and deployed in 1972 in limited service with the Special Forces of the Italian Army, and a few other customers.

The AR70/223 was the civilian version.

So, yes, the AR70 is a correct period weapon for the movie era.

Some of Vernon's South African slang was not in use in the 1970s.

The film is set in the 1970's but Justine uses a Taurus Model 85 revolver which was not manufactured until 1985.

The red van is a much later model. The grille is wrong and 1970's Chev vans would have the ignition on the dash not the steering column.

Frank refers to County Down as being in "Northern Ireland". An Irish republican would not use that term, as it would give recognition to British rule in Ireland.