At 320g it should be eating rat pups or adult (big) mice. Mine at 9 months has 380g and is eating 30-35g rat pups on a weekly basis
There's a guideline to feeding. Pray shouldn't be wider than the widest part of the snake and preys weight should be around 10-15% of snakes weight.
Hope this helps.
P.S. mine had a diet of a little chick also, since there were 2 weeks i couldn't get any mice or rat for him. Haven't had problem. He took the chick almost instantly.