Difference between 20 and 30 yd pins downrange

[RIStrutStopper]

Okay, this isn't really technical and I know there are alot of factors that would contribute to this, but I'm just curious. If I have my sight set on my 30 yard mark (equivalent to 30 yard pin for those with multiple pin sights) and at 20 yards I hold dead on the bullseye, my rig shoots approximately 6 inches high. A friend with a similar poundage bow (albiet with a longer draw length) did the same thing, and his difference between 30 yard and 20 yard pins is only about 1 inch (he could group in the white regardless of which pin he was using). My question is, if you took a shot at the X ring at 20 yards with your 30 yard pin, how high does your rig shoot?

[Bulzeye]

It will vary greatly.
Depends on arrow speed/weight.

[Straightarrow]

Depends on arrow speed/weight.

Actually it will vary depending on speed and drag. Weight will have no direct bearing on it.

The following will give you an average drop between 20 and 40 yards

Spread of arrow drop between 20 and 40 yard group

Speed (fps) Drop in inches
220 28.7
240 24.2
260 20.6
280 17.7
300 15.5
320 13.6

As you can see there is only 5" difference between 260 fps and 300 fps. It less than half that from 20 to 30 yards. Hardly something to worry about. Much greater deviations can be obtained by shooting a too light arrow that has too low an FOC or too lightly spined. The quest for speed can indeed come at great cost and little benefit.

[TFOX]

I am about 4" high @ 20 yards with my 30 yard mark.I have a hard time believing that your friend wasn't, at the very least subcontiously adjusting the pin and aiming a little lower.1" difference is really flat.

[Arthur P]

Another variable is parallax, the distance from the peep sight to the arrow at full draw. Someone with a short face or anchoring high up on his face, will have a short parallax and will have a greater difference between his 20 and 30 pins than someone with a long face or using a low anchor.

[RIStrutStopper]

[quote]ORIGINAL:

Actually it will vary depending on speed and drag. Weight will have no direct bearing on it.

This makes sense. Intuitively (without breaking out the old physics books) It doesn't matter how heavy something is, gravity will have the same effect on any object regardless of weight. Drag will counter the effect of gravity though (a feather and a hunk of lead won't fall at the same rate due to air resistance or drag). Also, drag slowing an arrow down horizontally should have an effect (slowing the arrow down allowing gravity to drop it further in a given distance because it took longer to get there). The weight of the arrow does come into play only because a heavier arrow will lower the speed also allowing the force of gravity to drop it further at a given distance. A million things (type of vanes, weight of arrow, arrow spine affecting flight, nocks, peeps, and assorted stuff on the string, etc.) can affect how far an arrow drops in a given distance. I was just curious what the average drop is for some folks who visit this forum. Maybe some tinkering is in order to try to get a flatter shooting rig...