Heavy/bull sporter is a barrel contour that is between standard sporter and light/med palmas. Typically used in hunting applications yet still has a thicker muzzle diameter (usually between .700-.800”) but still necks down ahead of chamber shank (unlike true “varmint” contours that don’t-remington’s varmint contour is not what most barrel makers’ varmints look like), and usually weigh 3.5-4 lb.
X-Caliber #5 or 6, Shaw #2.5, Shilen #4 or 5, Krieger #5, Bartlien #3b, Brux #5, Remington Varmint, etc, are examples of heavy/bull sporter contours.
Your Shilen #1 is the opposite end of the sporter spectrum. Thanks for asking.