Some of you have asked if the TRUE line of sight/Scope Height changes from venue to venue.
The truth is that it does. And it all comes from the way scopes work.
People think that the vertical movement of the lenses is what changes the optical path, and therefore changes the target image location in relation to the scope's tube, which changes the relation to the bore.
NOT SO.
What the turrets change is the ANGLE at which a lens receives the rays from the previous lenses.
Because of this, the TRUE LOS/Scope Height CAN and DOES change every time you make a zero-reset.
Sometimes this change is small, sometimes it is not so small. It does depend on how far from optical center you start with, but at times the true LOS height seems to change a lot.
Well, there is an easy procedure to get this number right with the P-P Calc app:
0.- setup your scope for the day. Make sure that everything is in focus and that you are comfortable with the clothes you have the stock setup you have and the scope setup you have. Moving any of these will affect the other, so once the Match starts, do NOT move any of these.
1.- Shoot a target at your zero distance and make sure you are well zeroed.
2.- Now shoot a target at your maximum yardage (usually 55 yards/50 meters) and make sure you have measured the drop correctly (either in physical dimensions, clicks or holdover in either mrads or Divs).
3.- Now shoot an intermediate point. Let's say that your zero is 35 yards, and your Max distance is 55 yards, then pick 45 yards. If you zero is 25 yards (this is a "near zero") and your max is at 55 yards, then pick 40 yards. Whatever is an intermediate point will work.
If you did your job well, the two BC's for these distances will be pretty close together. Not exactly the same, but pretty close together.
4.- Now shoot a 10 yards group and note the position either in clicks or holdover.
Go back and save all this data.
Now display the POI graph.
You will notice that the curve is smooth and passes through the yellow circles for the zero, the intermediate point and the Max point.
Extrapolate to the vertical axis (Zero distance) and you will have measured the TRUE Scope / LOS height for that shoot. Plug in that number and then all the BC's should click in place and be very close together.
ALWAYS put MORE TRUST in the long range data than in the short range data. I would NOT endorse a Zero shorter than 30 yards, except for pistol.
If you get very discordant results, then re-shoot the targets starting with the long range ones.
Life is nor perfect and having problems at the sighting-in range is no fun. So get there early and do things slowly, methodically, and as well as you can from the first time.
Getting in a hurry will only slow you down.
Hope this helps!
The truth is that it does. And it all comes from the way scopes work.
People think that the vertical movement of the lenses is what changes the optical path, and therefore changes the target image location in relation to the scope's tube, which changes the relation to the bore.
NOT SO.
What the turrets change is the ANGLE at which a lens receives the rays from the previous lenses.
Because of this, the TRUE LOS/Scope Height CAN and DOES change every time you make a zero-reset.
Sometimes this change is small, sometimes it is not so small. It does depend on how far from optical center you start with, but at times the true LOS height seems to change a lot.
Well, there is an easy procedure to get this number right with the P-P Calc app:
0.- setup your scope for the day. Make sure that everything is in focus and that you are comfortable with the clothes you have the stock setup you have and the scope setup you have. Moving any of these will affect the other, so once the Match starts, do NOT move any of these.
1.- Shoot a target at your zero distance and make sure you are well zeroed.
2.- Now shoot a target at your maximum yardage (usually 55 yards/50 meters) and make sure you have measured the drop correctly (either in physical dimensions, clicks or holdover in either mrads or Divs).
3.- Now shoot an intermediate point. Let's say that your zero is 35 yards, and your Max distance is 55 yards, then pick 45 yards. If you zero is 25 yards (this is a "near zero") and your max is at 55 yards, then pick 40 yards. Whatever is an intermediate point will work.
If you did your job well, the two BC's for these distances will be pretty close together. Not exactly the same, but pretty close together.
4.- Now shoot a 10 yards group and note the position either in clicks or holdover.
Go back and save all this data.
Now display the POI graph.
You will notice that the curve is smooth and passes through the yellow circles for the zero, the intermediate point and the Max point.
Extrapolate to the vertical axis (Zero distance) and you will have measured the TRUE Scope / LOS height for that shoot. Plug in that number and then all the BC's should click in place and be very close together.
ALWAYS put MORE TRUST in the long range data than in the short range data. I would NOT endorse a Zero shorter than 30 yards, except for pistol.
If you get very discordant results, then re-shoot the targets starting with the long range ones.
Life is nor perfect and having problems at the sighting-in range is no fun. So get there early and do things slowly, methodically, and as well as you can from the first time.
Getting in a hurry will only slow you down.
Hope this helps!
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