Can a Winchester 12 ga defender shotgun be converted for small game hunting?

in most states it is legal to use if the magazine is plugged to hold only three cartridges. A piece of wooden dowel cut to the appropriate length works well.

Depending on your state law, you may need to plug the magazine to limit the number of shells that can be loaded. Some states limit you to three total in the gun - some have other limits. Gunsmiths sell the necessary plugs and can install them. If you have a pistol grip stock, you may find that unsuitable for hunting.