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Discussion Starter #1
I have an Excalibur Matrix Bulldog 380 crossbow that I am about to sight in using a HHA Tetra dial (newer version of the Optimizer Speedial). According to the instructions I am to sight in at 20 yards and then estimate the proper speed setting to hit bullseye's elevation wise for the 60 yard zero.

This will be my first time shooting a crossbow and messing with arrows, and I am trying to prevent missing the target and damaging an arrow at 60 yards by getting a good idea of what type of speed I'm getting.

The 380 designation means it is suppose to shoot the factory 350 grain arrow with field tip at 380 fps, although as I understand it this is most likely to only happen on the best of days and most likely is shooting a bit slower. The crossbow also came with some vibration/sound dampening devices installed which slow it down a bit and I am also using a custom Flemish string that is a bit slower than the factory one. In addition and most significantly, I will be shooting a heavier arrow with a total weight of approximately 450 grains.

I have read that a general rule of thumb for velocity vs arrow weight is that for every 5 grains added one looses 1 fps with the arrow. So this would roughly account for 20 fps slower, not sure how much to give weight to the other factors to get a better idea of what velocity to set it for for the first shot at 60 yards after a good 20 yard zero. Any help would be appreciated. Thanks.
 

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Normally one would not attempt the 60 yard shot after a 20 zero due to losing arrows especially with a unknown setup. I work out to the 60 yards by moving to 30, 40, 50 to confirm using trail and error. There is always going to a great amount of fall off from 40 to 60 yards as the speed of the arrow slows.
One could also get some ideal of the arrow trajectory by using a ballistics calculator found of the net.


good luck!
 

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I have never missed the target. I don't worry about speed just set speed dial close to advertised speed. Shoot bow in at 20 yds when it's zeroed at 20 I move to 40 shoot at the top of target with 20 yd pin,cross,etc. If it's a slow bow stack two targets on top of one another. After you shoot at 40 with 20yd sight in the arrow will be low. Just secure the bow with 20 yard cross on where you shot and turn the speed dial until it's right on the arrow you shot.you should be set. No chrono needed the scope has to match where bow is shooting not the chrono speed. If I am telling you wrong someone will correct me but that's the way I do it from others instructions. You can do the same thing shooting at 30 yds I was always told to go from 20 to 40. Hope this helps not good at explaning things so might have to get others to chime in best this old man can do.
 

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Your speed will likely be under 360fps with that heavy of an arrow. Like has been said.....shoot 20,30,40,50,60, and learn your bow and scope. Dont just start flinging arrows at 60 yrd.

Good luck
 

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Just use the desired arrow weight that your going to stick with to sight in your bow with. Start at 20 yards then back up to 30 and so on, until you have them all hitting zero. Then stick with that arrow weight and you'll be good to go. Try out diferent broadheads to find the one you like that hits the same spot your field points do..
 

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I've actually found that for every 2 1/2 - 3 grains you lose 1 FPS.. YMMV

Mike
 

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Discussion Starter #7
Thanks for the responses. Yeah I am reluctant to go from zeroing with my hunting broadhead at 20 yards to shooting at 60 yards, but that is what the instructions state for sighting in the HHA Tetra XB dial.

I am using a red dot reflex sight with the dial so there is only one aim point in the sight.

I'm very familiar with trajectory when it comes to firearms but am new to arrows. Can someone recommend a good arrow ballistics calculator that would give me a rough idea of what kind of drop I can expect with a 20 yard zero, at 30, 40, 50, and 60 yards? Would the arrow usually have already peaked around 20ish yards and pretty much be dropping continually from 30 yards and beyond? Thanks for the help.
 

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Discussion Starter #8
Your speed will likely be under 360fps with that heavy of an arrow. Like has been said.....shoot 20,30,40,50,60, and learn your bow and scope. Dont just start flinging arrows at 60 yrd.

Good luck

Yeah I'll definitely be below 360 fps. Just don't know if I'll be closer to 350 or 330 fps and how much of a difference that will make at 30, 40, 50 and 60 yards.

But yes, it makes all the sense in the world to work my way out at least a ways past 30 until I get a better idea of drop.

Do you happen to know a good arrow ballistics calculator?
 

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Discussion Starter #9
Normally one would not attempt the 60 yard shot after a 20 zero due to losing arrows especially with a unknown setup. I work out to the 60 yards by moving to 30, 40, 50 to confirm using trail and error. There is always going to a great amount of fall off from 40 to 60 yards as the speed of the arrow slows.
One could also get some ideal of the arrow trajectory by using a ballistics calculator found of the net.


good luck!
Thanks, do you know of a good arrow ballistics calculator online?
 

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Discussion Starter #10
Just use the desired arrow weight that your going to stick with to sight in your bow with. Start at 20 yards then back up to 30 and so on, until you have them all hitting zero. Then stick with that arrow weight and you'll be good to go. Try out diferent broadheads to find the one you like that hits the same spot your field points do..
Thanks. I forgot to mention it's a red dot sight so only one aimpoint in the sight, that's my main reason for the Tetra dial to begin with, as a scope is unfortunately not legal for me to use.

I will definitely be using the same 450 grain arrow setup, doing the initial shooting with field tips and then fine tuning with QAD Exodus broadheads assuming they shoot well enough.
 

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25gr of weight is roughly 10fps. Add 25 and lose 10fps. That’s a rough way to estimate speed
 

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Discussion Starter #12
25gr of weight is roughly 10fps. Add 25 and lose 10fps. That’s a rough way to estimate speed

Thanks for the response, so increasing the arrow weight by 100 like I am would drop my approximately 40 fps, putting me at 340 fps with just the arrow weight alone, not to mention the other potential factors.
 

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I always take my first shot at 10 yards when I am sighting in a new scope. I have seen way too many misses at 20 yards on the first shot. I also aim almost at the bottom of the target because I would rather hit the ground and bounce into the target than shoot over it. I have never missed though at 10 yards.
 

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Yeah I'll definitely be below 360 fps. Just don't know if I'll be closer to 350 or 330 fps and how much of a difference that will make at 30, 40, 50 and 60 yards.

But yes, it makes all the sense in the world to work my way out at least a ways past 30 until I get a better idea of drop.

Do you happen to know a good arrow ballistics calculator?
This is the best one I have seen as an example for my Ripper 415. It allows for variations. Check it out! The website is shown in lower left corner of the graph.
20200422_105842.jpg
 
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Discussion Starter #18
I always take my first shot at 10 yards when I am sighting in a new scope. I have seen way too many misses at 20 yards on the first shot. I also aim almost at the bottom of the target because I would rather hit the ground and bounce into the target than shoot over it. I have never missed though at 10 yards.
Good advice as usual; I will follow it. Thank you.
 

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Thank you, that is really helpful.
You are welcome! That's what we do on this site...help. I use that program for all my weapons.
Another tip on setting a scope before you send the first shot. For my crossbows I purchased a 308 laser cartridge. I lay it in the flight rail and use it to align the scope crosshairs at about 10 yards. That's the way to make sure of hitting the target at 10 yards. There are low cost also.
 

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Buy a chronograph ... and be done with it. :)
 
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