I just put a new sight on and I remember a guy at a archery shop had a measuring tool. How it worked was by sighting it in at 20 yards they would use that as a focal point then give you the gaps between the 30 and 40 yard pins. I know its not perfect but a good starting point. Anyone ever seen this?
It can be done, but I don't set a sight up that way..... I capture the ballistic advantage of an arrow and usually set a sight at 22 - 25yds for the first pin, getting the height the arc rises above the Line of Sight helps me decide where the pin can be most effectively used. You can do this one of two ways. You can use a ballistics calculator (the easy way that I use nowadays, or you can shoot the bow, noting the variation up and down from say 7 - 30yds. Then figure the best set-up point, the way I used to do it. For MOST bows that shoot between 265-290fps, it seemed that 24yds was almost ideal, and the arc height above the line of sight once the arrow met the line of sight is between 1.5-2" between 7 - 24 yds. This means you can get out to 26yds pretty safely on the first pin, even shooting 265fps. Setting the sights the way I set them, I usually get to 40yds on 3 pins with a safer distance judging error. From 24 to 32 yds at 265fps the arrow drops roughly 5" the same that it drops from 20-30yds, but from 32-40yds you get roughly 7" drop shooting a 265fps set-up, where fron 30-40 you have over 9" of drop to account for. Shooting something in the 280-290 range shortens the drop a fair bit, but there is still drop to account for. At 285fps, it's about 4.4" from 24 to 32yds, and from 32 to 40 it's 6.4" drop, where 20 to 30 is 4.7", and 30-40 is 7.8". These setting are good for both 3D AND hunting, and may keep a potential brisket shot up in the lower heart lung area and result in a quick kill rather than a LONG miserable fruitless track job!!!
Same theory that sight tapes for target sights are based on. If you know the speed of the bow you can select a tape that is close, sight the bow in for a certain yardage and affix the sight tape to that pin setting and the rest of your marks are close for the other yardages. The better way is to set two pins, one at 20 and one at say 50 or 60 and then choose the tape that has the matching gap for those two settings. I still do it old school and shoot each yardage individually. Knowing my bow's set-up allows me to guess the pin gaps in pretty close from experience and then I just fine tune each one from there. My fear is, and I speak from experiencing with bore sighting in the gunshop with more than one customer; a guy sets his sight and shoots at 20 yards in the shop. He uses a sight tape or program to set the rest of his pins out to 80 yards. Then he thinks he can go out and hunt/kill stuff at whatever yardage just because he has a pin set for it. I've had guys claim to shoot at animals at 500 yards with a rifle even though they've never even shot paper over 100!! Shooting a bow at 40 is NOT the same as shooting one at 20, I don't care if the sight is dead on perfect!
KodiakArcher's got it. Record each good shot - take your time here. You will end up with the most accurate sight tape and get to know all the subtle nuances of your bow/arrow set up. Make sure to record draw weight, brace and tiller height. Keep in a journal. While you're at it, pick up a decent (but not necessarily expensive) scale - something that displays .1 g (you can convert to Gn by multiplying by 15.4325) and make sure your arrows are the same weight. If you want to try the computer generated tapes as a place to start, try XSight, it's free: http://www.huntsvillearcheryclub.com/ Click free software.
That's exactly what I was referring to thank you. I would never use this and assume my now is on, I wanted to use it as a starting point. Gonna try it and test it out. I'll let u know how accurate it is. Thanks again!!
