The 16-gauge (Note how it's spelled) shotgun shell will hold slightly fewer pellets (small BBs). It will have slightly less recoil, but the difference will be so small that you might not notice it. Some 16 gauge shotguns are built lighter and smaller than the 12-gauge versions, but that is not always true. And you should know that today 16 gauge ammunition is less common than either 12 or 20 gauge. 30 or 50 years ago, 16 gauge was very popular but now it is getting rare.
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