I'm thinkin' that the revolver is a Colt 1863 "Navy", thought it could be any of the Walker Colt inspired designs, including the "Dragoon." With the simplified form and lack of identifiable details- aside from an open cylinder frame and distinct barrel shape-, it's anyone's guess which one it is.
I heard that there were and still are companies that offer conversion of the 1851 Navy to metallic cartridges...... the modern conversions would chamber .30 Special...... I wonder if that covers +P and +P+ loads.