I sight in all my guns at 100 yards. What I do is get either a large piece of brown paper 4x8 or tar paper and put a target in the middle. Than go to the range and use duct tape to secure in at 100 yards and start plinking away. I have a gun vise but I tend to hold the rifle steady using my tool box from the muzzleloader and a towel on top. This way I can see where my shots are hitting and adjust them accordingly. If the deer are less than 25 yards, than I aim a little high, knowing that my sight is higher than the barrell.

Good luck....

Tomster