What’s your nozzle diameter? Larger nozzles will clog less with composites.
Heat creep can be an issue with metal fillings, maybe try dropping the temp a little and/or increasing your hot end cooling.
Also 300 is probably not a great idea for PLA. You might now have some charred plastic in the nozzle that won’t be helping. You might want to pull it off and have a look/clean it out.
