Thanks for the reply. I am a member of the UKTC (United Kingdom Tank Club) and most members use blank firing pistols but the noise they make is totally unrealistic. I'm not wanting to fire a projectile from the barrel, merely simulate the deep bang and flash/smoke.
I've heard you can get stage special effect (cant remember their name) which might do the trick, but I'm curious what this society can suggest as I know nothing about the potential of pyrotechnics in this respect.