I have a .458 SOCOM barrel that is 10.5" long, and it is presently mounted on my CAR-15 gun (which is registered on a Form 4, so I can have a short barrel on it). I have to admit that I've only fired 4 cartridges through it, but it worked fine and I hit what I aimed at. The recoil was not anything to write home about. (Actually, my first shot(s) were with the gun on "auto" and it fired 2 cartridges so fast I could hardly tell there were 2; the muzzle stayed on target, too. I was impressed.)
flashguy