Per Magpul's fit notes it will accommodate a bull barrel. Here are more specifics provided by Magpul:
"Accepts ALL factory Remington barrels including VTR triangular barrel contours
Compatible with aftermarket barrel profiles up to a Medium Palma (0.920" dia. 5.50" forward of the breech)"
It won't fit a straight tapper barrel like the #7 Douglas or Shillen or the 3 1/2 tapper of the E R Shaw.