What all could cause a gun-mounted scope to be off sight?
Random brain-dead question, lol
... the scope wasn't aligned correctly when mounting ...
Bumping it, screws not being tight enough...
the recoil vibrates and re adjusts them
The screws aren't properly tight, dropping it or whacking it on something, scope wasn't aligned with it, or the gun just sucks... LOL!!! xD
Dropping it, banging it on something, reticle broke, or loose mounting screws.