I bought the Bushnell one. You need to be in somewhat low lighting ie early morning or late afternoon. In bright daylight, I couldn't see it at the 50yrd mark.
You can try this method if it's bolt action rifle, unloaded of course.
- Setup rifle on a benchrest or bipod so that it is stable.
- Remove bolt from rifle
- With your eyes about 6"-8" away, look down the bore of your barrel and line it up with the target ahead so that it is pretty much in the center of the sight picture.
- Without moving the rifle, sight down the scope and adjust the crosshairs so that they are on the target in your sight picture above.
- Pick a point on your target and fire a round. You'll be surprised at how close you can get.
- Reset the rifle, centering the crosshairs at the same target you shot at above. Without moving the rifle, adjust the crosshairs moving it to the point of impact.
- Fire another round at the target. You should be be pretty close or if not on the mark. Shoot 3-5rnds for an average. Fine tune if needed.
Edit: Ah crud, forgot this was in the Black Rifle section. Ignore the above. Go buy a boresighter. lol