sighting in distance

[predator11]

I personally would not be comfortable shooting at deer over 30 yards. My crossbow is rated at 250 fps. What distance should I sight the red dot on. My scope has only one dot.

[smokeeter]

Predator, sight in the red dot to be dead on at a distance you feel most comfortable, ie. 30 yrds.
hold low @ 20yrds and high @ 40yrds.
With my excaliber, the hold over and under at those ranges , is 10 inches.

[kansas]

Sight in at the distance that most of your shots take place. It may be 20 or it may be 25. You want to make sure that you are your most accurate where most of your shots take place. It makes little sense to sight in at 20 if 75% of your shots are at 25.
Kansas

[edge]

IMO,

You need to know the velocity of your bolt ( arrow ), and the distance that the sight is above the bolt.

As a "General" rule of thumb, a single pin on a bow will be good from zero yards out to 0.3 times the velocity in fps

Eg: 300 fps x 0.3 = 90 ft or 30 yards
250 fps x 0.3 = 75 ft or 25 yards, etc.

This assumes that your sight is approx. 3 inches above the bolt centerline.

Since your bow is rated at 250 fps, I would set the sight at 25 yards and compensate out past that distance. Since you stated that you would not be comfortable past 30 yards, there should not be the need for much compensation anyway.

edge.

PS If you are shooting from a treestand, then distances closer to you than your stand is high will require substantial compensation for drop, but that is a totally different matter

As an afterthought, the B.C. of an arrow is somewhere around 0.090 +- depending an a huge number of factors with fletching size,helix, and feathers or vanes being big contributors. You can plug this into your ballistic software IF it will accept a velocity as low as 250 fps. ( RSI will, Point Blank will NOT )
edge.

[edge]

In my earlier post I had stated the B.C. incorrectly @ 0.90 instead of 0.090, sorry ;D

I have corrected the earlier post!

edge.

[predator11]

Ok guys a little more complicated than I thought but doesn't a crossbow bolt act much the same as a bullet as far as trajectory goes? It should cross the line of sight twice. So that should mean it crosses once at close range and a second time at the zeroed range. The only way I have of determining this is by shooting at various ranges. Do you suggest 5 or 10 yard increments or will this have to be decided by shooting also? It seems to me that there should be a distance that I can zero on that will just let me hold in the middle of the deer and score a fatal hit. I use a range finder so I know the distance.

[edge]

predator11 said:

SNIP
It seems to me that there should be a distance that I can zero on that will just let me hold in the middle of the deer and score a fatal hit. I use a range finder so I know the distance.

IMO, with a bow, THE shot is the Heart shot, and NEVER the center of the deer.

You should look at some slow motion camera footage of bow shot deer to see their incredibly fast reaction times!
A deer that is shot at more than a few yards can drop its full body height in about 1/10th of a second and your arrow may fly right over its back. Sight and sound are the key.

Back to your question of the crossover, and yes it is like setting up a scope on your rifle. Figuring the MPBR ( maximum point blank range ) needs three items to calculate:

1) velocity ( 250 fps );
2) Ballistic Coefficient ( 0.090 );
3) Height of the sight above the arrow centerline!

IF your sight is 3 inches above the arrow centerline AND the initial velocity is 250 fps,AND you sight dead on @ 25 yards,

THEN: the arrow crosses the line of sight at 4 yards and 25 yards. It will be 3 inches high at 15 yards and 3 inches low at 29 yards.

edge.

PS the arrow will be 9 inces low at 35 yards and 16 inches low at 40 yards, but these were further than you felt comfortable anyway

[predator11]

Edge you are correct, at 35 to 49 yards there is a lot of drop plus the reaction of the deer to the shot. I have never shot a deer with a bow or a crossbow but have seen films of deer "ducking" the arrow. I would rather have them within spitting distance and this will be difficult as I hunt exclusively from the ground. However I will try the 25 yard zero. I have taken 3 shots with the crossbow and it is 4 inches high at 15 yards right now so I will shoot it at the further distance as soon as I can get to the range. My thanks to everyone who replied and all the answers made sense to me. Just have to get some experience.