Speeder,
First, what are your intended use for this shotgun?
If for home defense, leave it alone and spend the money on proper training. #6 shot is just about perfect for in-home use. Muzzle blast will make you deaf and at night virtually blind for a few minutes. Training will prevent it being snatched and used against you as well as mitigate the hearing and vision loss aspects.
If you want you can pick up a hunting barrel and shoulder stock inexpensively for that purpose.
If you are really into zombie phobia, then all advice is useless as you have already given up on reality.
