If it's the actual practical sound of the prop igniting then it would be an extremely rare and cheesy element in an otherwise high-end (for the time) special effects movie. In my multiple decades of film and television work, I can't recall even once time when a special prop's practical sound was used as the sound in the finished mix.
The post audio folks would likely have mixed out whatever actual sound the gun made when ignited (regardless of whether it sounded interesting as-is) and replaced it with a sound effect that they could mix, process and modify to whatever level they needed to sound the same in every shot DESPITE the acoustics of the set, angle/placement of the gun with regard to the mikes, and other inconsistencies during shooting.
It's very difficult to control practical sounds - and just about every prop you see in a film or TV show is as silent as possible. If it's absolutely necessary that a prop make a noise, it would have caused the on-set sound person and the post folks some headaches when they had to replace it. They might have used a sound effect based on the way a flame ignition device might sound, but I'd be very, very skeptical if anyone has been told that we're hearing the practical sound of the actual prop in Logan's Run. If it's the actual sound of the gun "enhanced" it would still have been added later. It's not impossible that they might have based the sound on the actual prop, but with all the time, changes, opinions, more changes, more opinions and more changes involved in things like sound effects and post production, I'd bet they created a sound from scratch.
Film and TV audio is very controlled - just like almost all other aspects of production. Back in the days when I was an on-set prop guy, I installed countless switches that turned off the cooling fans in countless gadgets to avoid even that small amount of on-set noise. Even mundane sounds are added in post. For instance when you see someone carrying a grocery bag, it's very likely "silent bag" which is made of a kind of material that looks just like a brown paper grocery sack, but doesn't make any crinkly noises when its handled. The crinkly sounds of the bag are added later so they can be mixed and processed.
I searched my vast archive of sci-fi sound effects and alas couldn't find a good sample of the Logan's Run DS gun.
