For the most part, pistols that are designed to use rifle cartridges are a novelty. The public thinks "hey, this is great! I'll have the power of an AR15 in a compact handgun size." The manufacturer know better, but they're just out to make money. The mechanics of rifle rounds require a certain length barrel to get adequate bullet speed. As an example, the 12ga needs 18" of barrel to reach maximum velocity; 20" for 3" magnum, if I remember correctly. If the barrel is shorter than that, you'll just blow unburned powder out the end of the barrel, powder that couldn't contribute to the speed of the load. The shorter the barrel, the more powder you'll blow out the end. A 10" barrel for a .223 would probably loose 1/2 it's powder charge out the end of the barrel. Like Ruger says, you could load up a .223 with faster burning powder, but you won't find any listings for that kind of load in any of the loading manuals, so you'd be flying blind. I made a friend of mine some "squirrel loads" for his 3030 one time. Used a 110gr bullet and 296 Powder. It worked really well. But I had researched other loads that had that much 296 exposed to the primer "loosely", and knew what my pressures would be. It could be done for .223, but it would require some research. Even then, you'd still be in the "magnum pistol" velocity range: 1,100-1,300 fps.