I have a stainless System-1 in 54 cal. It is very similar to the black diamond other than the removable barrel. A friend of mine hunts exclusively with a system-1. They tend to be good shooters but are a little bit of a pain to take apart to clean. I believe they were discontinued a few years ago but there are still several on dealers shelves. You can get barrels in 32, 50, 54 and 58 cal as well as 12 ga shotgun. I hardly ever use mine so I can't speak for their long term reliability. I do have concerns with the 2 little allen bolts that hold the barrel in place. If they work loose I would expect poor accuracy and possibly a dangerous situation. If you have a burning desire to have 1 gun with 50 and 54 cal barrels its not a bad buy. If you can live with 1 caliber I'd look into a black diamond or a knight.