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The method I gave for cutting distances up/down hill is very crude, but with some practice works out pretty well ... A Marine Gunny Sgt gave me that tip for battle field conditions and I've used it with good effect on several cow elk using a .30-06 as well as 6x6 Bull at about 40 yds 30º down angle using a bow when I'd left my rangefinder back in camp. However, if you want to be more precise for competition, then you'll need an inclinometer and a cut sheet.
: This reads out the angle. The problem with inclinometers is that they are expensive $$$$ and if they have increments marked in the viewer, may be disqualifying. Of course, angle compensated rangefinders would also not be allowed. So, here is a cheap DIY inclinometer: Cut a 3.75" disk out of 3/16" thick polycarbonate and drill a center hole. Next, drill and tap a small hole anywhere on the edge for a 2" machine screw. Add lead weights to the machine screw and screw into the disk. Take 12" of 3/4" aluminum angle, cut into 8" and 4" section. Drill a hole in the 8" section near one end, and drill a small hole 2" on center from the first hole for a small nail pointer to be epoxied in place. Drill a 1/8" hole in about the middle of the 8" piece and pop rivet the 4" section in place for the folding handle. Paint the pointer red and the end of the 8" piece near the disk red, or some other color to help as a visual aide. Hold the inclinometer and sight level, mark the zero angle on the edge of the disk. Make a 3" x 3/16" tape and mark it off in 10º major increments and 5º minor increments (0º to 45º will be 1.5", each 10º increment will be 1/3rd inch ). Adhere the tape to the edge of the disk aligning the zero marks. Now all you need is a cut sheet.
: The easiest way to make a cut sheet is with OnTarget2 SFA, TAP, or AA software. Here are a couple of my OT2 cut sheets. As you can see by comparing the 322 fps chart to the 263 fps chart, the arrow speed is so much greater than Gravity's vectors that even a difference of 60 fps doesn't really change the cut distance by more than a few inches of range. If you don't have software, you could safely use one of these sheets. Notice, since some of Gravity 'pushes' the arrow on the downhill, the downhill cut is greater than the uphill cut where some of Gravity 'pulls' back on the arrow speed on the uphill.
But, as pointed out, when very, very close, parallax outweighs arrow speed or effects of gravity. The best way to get your sight settings up close is by Trial & Error. Straddle a line 6' from a target with a dot the size of a pencil eraser and find what yardage hits the dot, repeat for 9', 12', 15', 18', and 21'. The angle or arrow speed won't affect the results. ... hope this helps.
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