between 300-450 degrees. if your asking about this for keeping ammo in a hot car, it does not get hot enough anywhere on the planet in any container to cause a primer to go off.
dont store ammo or guns in microwaves or ovens or any other appliance. yes morons have done it and killed people storing guns in ovens
"Gun control: The theory that a woman found dead in an alley, raped and strangled with her panty hose, is somehow morally superior to a woman explaining to police how her attacker got that fatal bullet wound." ó L. Neil Smith
The problem with being stupid is you cannot simply decide to stop doing dumb things...
"I crapped my pants to avoid the draft!!" -Ted Nugent