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I have been playing around with TAP, trying to get my real world measurements to match up with the numbers I have plugged into TAP.

Here is my scenario.
Hoyt Razortec 29" @ 65#
SME Epsilon arrows @ 28" 4" vanes, 100gr tips (385gr total weight)
I know that the bow is shooting right around 270-272 fps
The sight paralax is 3"

Given that info, when I plot the arrow ballistic data, it shows for a sight zeroed @ 20 yards, that when shot into a target @ 8 yards, the arrow should impact approx .53" high.
Using a pin sighted for 30 yards, shooting into a target @ 8 yards, the arrow should impact approx 2.14" high.

Seems pretty simple...right?

Well here is the catch.
Using my 20 yard pin for an 8 yard shot, the arrow impacts approx 1.75" high.
Using my 30 yard pin for an 8 yard shot, the arrow impacts approx 2.75" high

It does not seem to make sense.

Using the initial numbers, and generating a sight tape yields a tape that is right on with my pins out to 50 yds, so I know the program is calculating things correctly.

What gives, I just can't seem to get my head around this issue.
 

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I'm not familiar with how TAP handles the parallax for close distance. With that in mind, how are you determining a 3" sight parallax? I know using AA that arrow speed, distance from center of peep to arrow at full draw, and distance from center of peep to sight pin are all needed to correctly calculate parallax sight settings (essentially those sight settings where you need to actually start moving the sight down the sight bar as you get closer rather than moving the sight up, somewhere around 10yd and in for many). Maybe missing something in your entry? Just a guess.

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At that distance your arrow may not have stablized so the oscilation of the arrow could cause the the high impact. Shoot through paper at 8 yard and see if you are tearing knock low.
 
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