Screen gunfire and screen impacts can be produced independently and combined into one apparent event. The visible source, the apparent consequence and the sound need not originate in the same physical action.
Separate visual elements
A muzzle effect identifies an apparent discharge. An impact effect changes the appearance of a target or its surroundings. A production can photograph, construct or add those elements separately.
Seven foam-latex T-1000 impact appliances have been catalogued as Terminator 2 production objects. Their existence documents one physical means of representing damage. It does not establish how every hit in the film was made.
John Wick: Chapter 4 used digital additions and augmentation for weapon flashes and impacts. A final shot can consequently contain a photographed performance together with damage that was not present in that form during filming.
Temporal connection
Sound joins the apparent source to the apparent consequence. A discharge sound, a material impact and subsequent debris movement perform different jobs. Their timing makes the separate elements legible as a sequence of events.
Take a constructed shot in which a weapon flashes and a wall changes appearance a moment later. Moving the impact sound to the flash changes the timing information even if neither visual element is altered. The depicted causal connection depends on the assembled sequence.
Object evidence and shot evidence
A surviving appliance proves that an object of that kind existed. A production account can identify where a method was used. A finished frame shows the combined appearance but does not necessarily reveal every contributing element.
The method must therefore be assigned at the level the evidence supports. “Practical gunfire” does not establish practical impacts, and a digital impact does not establish that the performer, weapon or surrounding set was digitally generated.