You need a 14” barrel to stay above the legal OAL on a 870 or clone like the Grizzly.
You are completely correct. If running a “raptor grip” on either the 870, or the 500, you need at least a 14” barrel to stay above the minimum length requirement. I was only pointing out a possible source for a short shotgun that no one had touched on. Short barrel AND mag fed to me says Grizzly, but the ones I’ve owned over the years always had a full stock, or the S&J 870 kit/rail system which kept them over required length.