The iron sights should be pretty close at 25. Take 1 shot and see where it is hitting, adjust accordingly and move to 50. Take shot 2 and adjust if necessary. 2" high at 50 seems about optimal. Shoot 2-3 at 50 shots to verify. You'll be about dead on at 100 if your group is 2" high at 50. Now if you have to make a small adjustment you can, but you don't need to shoot. Your irons are only for back-up if your scope fails if I understand correctly.
Do the same routine with the scope, after boresighting. This is done easily enough by putting the gun in a vise and looking through the bore, and centering a small object at 25 yds. Crank the crosshairs onto the object. If you don't have a vise you can take a cardboard box and cut notches to hold the forearm and the stock. You just need the gun to be still. Once you are 2" high at 50, go ahead and shoot a group at 100.
You shold be done by shot #10-12, and still have powder enough for hunting. This all assumes you are shooting a bullet that your gun shoots acceptably.