Sighting for 100 yards when I only have 25


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Old 02-18-2014, 03:47 AM   #1
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Default Sighting for 100 yards when I only have 25

Just finished my first 300 Blackout build and mounted a Vortex Crossfire 2x7 on it. I was hoping someone could help me with a question I need answered before this weekend. If I only have the opportunity to sight my AR at 25 yards, how high above the POI do I have to sight the crosshairs on a paper target for it to be within less than inch between POA and POI at 100 yards? Any info anyone can provide would be greatly appreciated.



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Old 02-18-2014, 03:54 AM   #2
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Try this.

http://www.shooterscalculator.com/ballistic-trajectory-chart.php?t=f630255c



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Old 02-18-2014, 01:36 PM   #3
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Well, since you did not give us a HINT about what BULLET you are shooting, would suggest you start about 1 inch BELOW the aim point. The bullet is still rising to the line of sight on most AR type firearms. And I have seen 300 Blackout run from 120 to 240 gr bullets at different speeds.

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Old 02-18-2014, 02:39 PM   #4
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Bullets rises when fired from a rifle? maybe? Bullets are rising down range? Not likely. Did Old Newton get his theory wrong? Or is this a long held shooting "Myth"?

http://www.chuckhawks.com/bullet_trajectory.htm

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Old 02-18-2014, 02:59 PM   #5
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Depending on the height of your scope rings the gun is going to shoot at least a couple inches high at 100 yards if you sight in at 25 yards.

You are not wasting your time sighting in at 25 yards. If you have the rifle sighted in at 25 yards it will only require a few shots to get the rifle dead on at 100 yards.

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Old 02-18-2014, 03:02 PM   #6
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try this http://home.comcast.net/~j_colt123/25%20Yard%20Aimpoint%20100%20Zero.pdf

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Old 02-18-2014, 03:17 PM   #7
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Nitestalker- bullets begin to drop the instant they leave the barrel- IF the bore is level.

However, as that article explains- almost every rifle will be tipped up to some degree. The bullets travel in an arc (a parabola) that passes upward thru the line of sight, and drops BACK to the line of sight at the target.

Except for my phased plasma rifle in the 40 watt range. It shoots flat.

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Old 02-18-2014, 04:31 PM   #8
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That whole gravity thing is confusing .

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Old 02-18-2014, 04:39 PM   #9
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c3,,, is that plasma rifle legal for elk and what would be the minimum wattage you would recommend?

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Old 02-18-2014, 05:50 PM   #10
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Quote:
Originally Posted by seancslaughter View Post
That is the perfect chart! Thanks for your input guys.


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