I have one in .223. I bought it when they first hit the market and other calibers weren't readily available. With a Vortex Scout 2-7x it's pretty accurate but man it is loud, but it's a 10" .223 so it's expected. I love the pistol, but I am going to rebarrel it to 6.5 Creedmoor. I picked up a large shank rifle barrel off the forum here that I'm going to have cut back to 14" and threaded. The only magazine I have used in mine is the factory one, but I have used an AICS single shot sled and it worked great.