It's a shortened 30 Remington case. Same size as a 30-30 if you turned off the rim. It'll fit in an AR-15 with just a bolt, barrel, and mag change. According to Remington they make one model of 700 and a couple model 7's in this caliber. I doubt it's too popular yet in bolt guns, though lots of AR shooters seem to like it. The reason I'm interested in it is you can make rimless 30 Herrett cases out of the SPC brass, and it ought to make a pretty good cast bullet round for bolt guns.