Range Report Check my math?

[trigger29]

OK. Here's the deal. I've found a 2000 yard range, where I may be able to shoot my .338 LM, but there's 2 irrigation pivots running through it. One at 675 yards, and one at about 1200 yards. Question is. Assuming a b.c. of .76, and muzzle velocity of 2800, if I were to shoot across the whole field, 2005 yards, could I just shoot over them? Here's what I came up with so far.

At 50 degrees and my altitude and zeroed at 100, this is what I get.

2000 yards would require 84.5 MOA up.
84.5 moa at 675 yards would be 597 inches up, or about 50 feet. - about 96" of bullet drop by that point, leaving me at about 42 feet high yet, clearing the first pivot.

The second pivot is at 1200 yards
84.5 moa= 1061" up, or88 1/2 feet minus 422" of bullet drop, leaving 639", or 53 feet. clearing the second pivot on the way down to the target. Is this anywhere in the ball park, or is my thinking all askew?

 

[trigger29]

Anybody? In 51 views, nobody?

 

[ericthebeard]

Gut check, without going through the whole thing... I'm a better analyst than ELR shooter, so take that for what its worth.

84.5 MOA * 1.05 = 88.7 inches of vertical over center at 100 yards. Times 6.75 (moving that 89" stacked over another ~7x away) you get ~599 inches. Basically what you got.

The problem is that this is only the linear component as the bullet JUST exists the barrel. It starts dropping and slowing down right away. So if you imagine a laser pointer coming out of your bore shooting infinitely off into the sky, that is what you just calculated. Over that you need to imagine what the bullet arc, in real flight, looks like and calculate the elevation of THAT arc (well, lenticular or catenary or whatever...).

I'd go to JBM online and play with the angles needed to HIT the targets you want to avoid and look at the total elevation on the gun (aiming angle + scope angle) and compare that to the angular solution needed for the "flat", 2000 yard shot.

See if it sticks...

 

[trigger29]

I deducted the bullet drop from that 597", being 96" of bullet drop, leaving me still up about 42 feet. Is this the same thing?

 

[MitchK]

Set the zero to 2000 yds in your calculator. Check the distances of the irrigation rigs and see how high the bullet is at that distance.

 

[ericthebeard]

Set the zero to 2000 yds in your calculator. Check the distances of the irrigation rigs and see how high the bullet is at that distance.

There's a slick solution... knew there'd be something like that out there.

 

[trigger29]

Set the zero to 2000 yds in your calculator. Check the distances of the irrigation rigs and see how high the bullet is at that distance.

Duh. I knew there should be an easy way. I was looking at JBM trying to make it calculate bullet path. My intelligence is just low today. Need more coffee maybe? Thanks man. I should have thought of that.

 

[bogeybrown]

I don't have my Kestrel with me, but I seem to remember the Atrag version calculating MaxOrd for you. I'd imagine at least some of the other ballistics programs could give you the ord/max ord at a distance?
The setting zero at 2000 is fricken BRILLIANT, many props to MitchK for thinking of that.