gonna buy a shotgun for both hunting and home defense. I found one at walmart, a mossberg 20 gauge with both smooth and rifled barrels for $280 bucks. Will the 20 gauge be plenty for both purposes or should I shop around for a 12 gauge? I also plan on taking it to the range to break my son in on firearms. thinking the 12 might be alittle much for him though. He is 5ft and about 100 lbs.