I can't definitely recall the chamber pressures involved, but I _think_ the .303 Lee Enfield (
) was 7 tons per square inch, and a 12ga shotgun around 3 tons per square inch... 6720psi is going to convert any plastic or diecast flare pistol into handgun McNuggets a few milliseconds after the hammer falls.
The shot load probably won't even have cleared the muzzle by that point.
