What do you guys think of this? It's a Windham Weaponry rifle that has 556, 300 Black, 7.62x39, and 9mm all in one AR system. Course not MD legal, but still curious.
https://www.windhamweaponry.com/firearms/rifles/mutli-caliber-systems/
https://www.windhamweaponry.com/firearms/rifles/mutli-caliber-systems/