Boa constrictor problem?

i have a 4 month old red tail boa, i doubt its a true red tail thats what the store said tho, any way i have a problem when im feeding him, he's feed in a diffrent container then his cage. i feed em in a rubber maid tub but when he's done eating he always bites my hand i give him a good couple min after he swallows his pry. he's feed frozen mice, hoppers at his stage and he normally eats two. how do i get him not to bite after feeding? i dont react when it happends he lets go pretty quick, its not painfull but when he gets big it pry will! so any help ideas? thanks