On the heat issue prolonged fire would cause the metal to soften allowing for increased degradation of the rifling.
The easiest ways for it to happen would be either a poorly made barrel or a barrel not designed for a specific projectile. Different barrel twist rates are better for different cartridges. A heavy bullet is better in a faster twisted barrel. If you fired a very heavy bullet in a slow twisted barrel you would likely not have it reach a proper stabilization.
On the heat issue prolonged fire would cause the metal to soften allowing for increased degradation of the rifling.
The easiest ways for it to happen would be either a poorly made barrel or a barrel not designed for a specific projectile. Different barrel twist rates are better for different cartridges. A heavy bullet is better in a faster twisted barrel. If you fired a very heavy bullet in a slow twisted barrel you would likely not have it reach a proper stabilization.