The book is a joke, but as far as joke zombie discussions like this one go it is THE authority for zombie material. every zombie hunter must have a copy.
but back to zombie slaying.
Personally I dont think his notion about no automatics is fully true. I mean yes head shots are the best but with a high powered weapon such as the L85, M-16, G36 etc etc shots to the body can create a great deal of trauma including breaking bones. So even if it really isn't dead yet it will be effective at incapacitating one. This is good especially if you aren't a marksman.