Some states have shotgun deer hunting zones, like southern Michigan. They were letting people use handguns in the shotgun zone here with certain caliber limitations. They had to be straight wall cartridges of a minimum of .35 caliber and a certain maximum overall length. The typical Magnum revolver rounds all fit that category. Muzzle loaders are allowed too. I don't know if the Maximum revolver cartridges were always allowed or not, but they are now, along with the .500 S&W Magnum. The .450 Bushmaster is just a bit longer than those, and now you can use a .450 Bushmaster rifle in the shotgun zone. And maybe nothing longer than a 1.7" case, but I'm not sure. If you're confused, you aren't the only one. There are other states that allow it too, but not bottle-necked cartridges most "deer rifles" use. That may be driving a lot of sales for the caliber. Given a choice to use a .450 Bushmaster rifle or a shotgun loaded with slugs, I know which one I'd rather use for deer hunting.