Hi there, the answer for you is yes. This printer will print on to 300gsm card.
Commercially available printers are designed to print on to anything from the poorest quality paper up to 500gsm, with a high quality printer like this; you should have no problem printing on to this weight of card.
Heavier card is usually classified as around 260-300 mgs and is used for heavy embellishment, for example on professional style wedding invitations.