No, because guns don't go off by themselves. Besides I believe it will damage t he gun over time, thick plastic rod sticking out of your barrel, with slide closing on it, barrel on a Glock tilts up and slide forcing foward. Do not like, sometimes crushes on the extractor.
Just keep your slide open so others can see.
SHTF vs TEOTWAWKI you ask? SHTF, just some crap on the ceiling and walls, TEOTWAWKI end of the world as we know it. Orignally made by 9mm/®™©