Re: What scope for my 338 Lapua
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Michael Aos</div><div class="ubbcode-body">The Premier 5-25x has 30MRAD / 103MOA on internal travel. Double-turn knob dials up to 27 mils for the automatic zero-stop.
Say 300gr Scenar @ 2700fps is ~23-mils / ~79 MOA to 2000yds from a 100yd zero.
How do I calculate the MOA base to get? 20 MOA? 30? 40 MOA?
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Google online ballistics software. If you have an iPhone, iPad or Android based Phone or Tablet there is some really great software you can download, one is called "Shooter".
To get a good idea if point of aim can be adjusted for a range, say 1760y, the ballistics software will tell you the bullet drop. In the case of Factory Lapua 338LM 300gr Scenar at 2750fps and a 300y zero (leaving out Atmospherics for simplicity) the bullet drop at 910y would be about 20MOA. So a 20MOA incline base would keep the scopes elevation adjustment near center. At 1500y the drop would be about 49MOA and at 1760y 67MOA. The 5.5-22x50/56 scope has 100MOA of internal elevation adjustment (top to bottom, so only 50MOA center to top). I need 67MOA to reach out to 1760y, but the scope only had 50MOA. With a 20MOA incline base I now have about 70MOA of elevation rise but that takes the same amount away from the bottom end.
So with a 20MOA base and a scope with a total elevation of 100MOA a 1mile shot should be with in range of point of aim, but just.
If you want to go out to 2000y with the same ballistics as above I show you would need 88MOA of elevation, so a 40MOA base would likely be needed.
Here is a good article explaining some basic optics and ballistics theory that covers this some,
http://demigodllc.com/articles/practical-long-range-rifle-shooting-optics/