I came across an older Mossberg 835 turkey gun in realtree hardwoods 20/20 with a 24" vent rib barrel. Somebody has removed all the sights from the rib leaving 5 empty holes one at about 1/2" from the muzzle another about 3" from the muzzle a third around 9" and two more at 17 1/2" and about 18" from the muzzle. Are these for securing the rifle sights or were these drilled and tapped by Bubba? I called Mossberg and they told me that all the sights they use are clamped on the rib and that the holed are not done by Mossberg. Did Mossberg use sights that were attached by screws at one time?? also if these holes are factory threaded does anyone happen to know the size and thread pitch so I can get some plugs for all these holes.