The young Blues centre-back will remain on loan at The Memorial Stadium until 18th April.
"After making his debut against Boston, Sam had a very good week of training last week and his performance on Saturday against Notts County was very good," Pirates first team coach Paul Trollope told his club's official website.
"For a young lad he talks and organises well, and combined with how quick and strong he is, we're very pleased to have him here.
"He's been a welcome addition to the squad over his first month, and we're delighted to have him with us for at another month."