a0cake
10-07-11, 18:45
Are you anal retentive? Need to know your exact sight height? This is for you. In all honesty, minor errors in sight height measurement will not greatly affect trajectory calculations. But some of us are driven by perfection, and thus we arrive at this method.
First, optically center your scope. You should be doing this anyway when you pair a scope with a rifle for the first time. Note: counting total travel in clicks then coming back halfway does not always optically center your scope. US Optics' recommended technique is a good way to do it. Go here http://www.usoptics.com/index.php?page=instructions and then click on "erector centering" to download the video.
Now that you've accomplished this, it's time to determine your sight height, or HOB.
The rifle I'll be using to illustrate this will be a BCM SS410 18'' AR. AR's make doing this a little unnecessary because it's easy to measure HOB, but this method is handy for rifles where it's not so easy to measure.
http://www.hunt101.com/data/500/2011-10-07_18-46-41_517_Medium_.jpg
First, turn your scope's magnification down as low as it will go. Then, take some tin foil and place it tightly over the Objective Lens of your optic. Poke a tiny hole in the center of the tin foil after it's placed over the optic. This will allow the scope to focus down to extremely close distances of around 12'' away. It will also decrease light transmission, so make sure you are in a well lit area.
http://www.hunt101.com/data/500/2011-10-07_18-44-25_341_Medium_.jpg
Next, make a small single dot with a marker on a target board or piece of paper. Place your optic's reticle on the dot you've drawn on the target board, with your muzzle touching the piece of paper or very close to it. (The tin foil will let your scope focus being this close)
http://www.hunt101.com/data/500/2011-10-07_18-45-23_897_Medium_.jpg
Now, fire your rifle. Measure the distances from the target dot to the bullet hole. That is your exact HOB.
You can also have a buddy trace around your muzzle and then measure from the center of the circle if you want to do this without firing your rifle.
Is this kind of stupid? Yes, probably. But, it may just be the most precise way to measure HOB. In an activity where fractions of an inch count, I see no reason not to use this method.
First, optically center your scope. You should be doing this anyway when you pair a scope with a rifle for the first time. Note: counting total travel in clicks then coming back halfway does not always optically center your scope. US Optics' recommended technique is a good way to do it. Go here http://www.usoptics.com/index.php?page=instructions and then click on "erector centering" to download the video.
Now that you've accomplished this, it's time to determine your sight height, or HOB.
The rifle I'll be using to illustrate this will be a BCM SS410 18'' AR. AR's make doing this a little unnecessary because it's easy to measure HOB, but this method is handy for rifles where it's not so easy to measure.
http://www.hunt101.com/data/500/2011-10-07_18-46-41_517_Medium_.jpg
First, turn your scope's magnification down as low as it will go. Then, take some tin foil and place it tightly over the Objective Lens of your optic. Poke a tiny hole in the center of the tin foil after it's placed over the optic. This will allow the scope to focus down to extremely close distances of around 12'' away. It will also decrease light transmission, so make sure you are in a well lit area.
http://www.hunt101.com/data/500/2011-10-07_18-44-25_341_Medium_.jpg
Next, make a small single dot with a marker on a target board or piece of paper. Place your optic's reticle on the dot you've drawn on the target board, with your muzzle touching the piece of paper or very close to it. (The tin foil will let your scope focus being this close)
http://www.hunt101.com/data/500/2011-10-07_18-45-23_897_Medium_.jpg
Now, fire your rifle. Measure the distances from the target dot to the bullet hole. That is your exact HOB.
You can also have a buddy trace around your muzzle and then measure from the center of the circle if you want to do this without firing your rifle.
Is this kind of stupid? Yes, probably. But, it may just be the most precise way to measure HOB. In an activity where fractions of an inch count, I see no reason not to use this method.