Fuzes are an art and science in themselves, and its likely WW3 fuzes may range from prewar techno-wonders to wartime rough-and-readys.
A fuze error killed an entire gun crew in Spike Milligan's war memoirs. The guns were in a box layout and a rear gun's round exploded about five yards from the muzzle, right over another crew. Evidently defective fuzes aren't too rare.
(By the way, weapons use 'fuzes' and electricals use 'fuses')
There's a lot of data on fuzes available on the net, I encourage any GM to look them up and see how many options the fuze gives a gunner. Also, go over to GlobalSecurity and look for '
big bullets for beginners'.