A seal seals an annulus in a subsea assembly between a wellhead and a casing hanger landed on a shoulder within a bore of the wellhead. The seal includes a casing hanger seal ring disposed within the annulus. The seal ring engaged with an inner diameter surface of the wellhead, and engaged with an outer diameter surface of the casing hanger so that the seal ring prevents flow through the annulus. A lockdown slip ring is secured to a lower end of the seal ring so that, when the seal ring is energized, the lockdown slip ring engages a substantially smooth inner diameter surface portion of the wellhead and a substantially smooth outer diameter surface portion of the casing hanger to limit upwards axial movement of the casing hanger.