First post here, so thanks for your patience. I have an early 1990's H&K imported Black Eagle shotgun. It's the slug version and it's nice for what it is, but does anyone know what barrels fit this gun? The barrel extension forms the upper part of the receiver like my SBE, but the barrel from my SBE doesn't fit it and it's not the same design as the newer montefeltros. Is the design unique to the original Black Eagle or will some other barrel fit?