Easily done by any competent gunsmith. Nothing special about the 77 vs. most any other bolt gun. Since it was a .243 originally it will be a short action if it is a MKII (not sure about the original 77). If he is loading from a magazine it will need to be the original 6.5/284 as opposed to the Norma version which seats the bullet longer for more case capacity (and thus too long for short action magazine loading).