Super 16 barrels have the same screw spacing as all other factory carbine barrels. Barrel contour is another matter. A forarm made for a tapered barrel will have to be "opened up" in order to fit a heavy(bull) barrel. Most custom barrel makers use the same screw spacing, but since it's custom that doesn't have to be the case either
. I generally use a forarm made for (or converted to) a full bull contour and when using a tapered barrel add a thicker washer between the forarm and barrel...leaves a little gap around the barrel which I like
. A short piece of wooden dowel and a little sand paper is all that is needed to "open up" the barrel channel on the forarm.
Walt