It is a single shot, stainless, factory, 15 inch TC encore pistol barrel. I am not sure of the MV and I do not own a chronograph. Swift publishes 1907 in a 8.5 inch barrel. This is what Swift says about their a-frame bullet:
Heavy Revolver A-Frame? bullets expand at 950 feet per second, to 1.65x their original caliber, and maintain 97% of their weight. They are virtually indestructible at velocities in excess of 3000 feet per second.?