This show, and I understand it’s just a TV show, indicated that the round was fired from a bolt action rifle. They did all sorts of convoluted simulations to “prove” it.
The British .303 round was used in both the standard service rifle, and the Vickers machinegun in common use by British, Canadian, and ANZAC forces of the time. No matter what convolutions they went through, the fact that the bullet was a .303 is essentially meaningless, without ballistics testing, which had never, and undoubtedly will never, be done. Once again, who knows?
the infowarrior