I have the exact same setup, light contour and all.
Make sure you follow the Hasting assembly instructions. There is one piece of the Remington assembly that you remove for this barrel. ( I think it is the barrel seal/activator )
Also Hasting notes that 2 3/4" shells may not eject. I have shot nothing but 3" shells in mine.
One final note, make sure you thoroughly disassemble and clean the gun to free up the action as much as possible.
Hope this helps....
-Tom