ballistic coefficient Arrows & Bolts

What are you guys using for BC in your calculations and trajectory programs?

 

didnt know that mattered in bowhunting deer and what traj. programs .............

 

I'm sorry sir, can you elaborate

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Trajectory is everything regards the vertical component of your aim and flight path. Tis why there are sight pins or crosshairs on bows.

There are programs that calculate for you. Some you can download and some you can use on a web site interface. You can even make a spread sheet to calculate this. I like my old DOS program. I need to fire up an XP box to use it since it is not compliant with the current 'gov wants to know and track everything you are doing' standards is the newer OS's.


Not to wander too far off topic but that is why backwards compatibility is lost with newer things now: because gov can't keep track.

Anywho, given the relevant parameters like speed, BC, ranges ....and minor things like altitude, temp humidity for very fine tuning .... etc it is not that complicated to contrast the flight path with the line of sight. Hitting high or low and how much at what distances given how you sight in. Very nice to know when aiming at a critter.

BC is pretty well documented for every popular bullet ( and keyed to the model used).

Arrow/bolt data is harder to find. BC can be calculated by shooting over your chrono at varying distances and using the change in velocity. The greater the separation the more accurate the value calculated. But chrono's have issues with lower velocities and not hitting the screens at long distances .... is a worry.

 

Who u callin' sir?

 

I guess I'm the odd guy out on this one. I just shoot at varying distances and adjust pins. But I enjoy data, please share anything you have.

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Anything? How many years you got?

But here, an example old file using BC = 0.110.

turns out the site will not allow a txt file ...

Lets see how a copypasta works out ....

Bullet : BC5 Zero : + 4.0 in. at 15.0 y
Weight : 396 grs Altitude : 700 ft
V0 : 300 ft/sec Temperature : 40 °F
BC : 0.110 Crosswind : 0.0 mph from 0°
L.O.S. : 2.8 in. above bore axis One click = 0.25in. at 100yds
─────────────────────────────────────────────────────────────────────────────
Range Velocity Energy Time Drop MaxH Path Drift Up Side
[yds] [ft/s] [ft.lbs] [in.] [in.] [in.] [in.] [ clicks ]

5 298 78 0.049 0.5 -1.0 0.4 0.0 -32.6 0.0
10 296 77 0.098 1.9 -0.6 2.7 0.0 -106.8 0.0
15 294 76 0.148 4.2 -0.1 4.0 0.0 -106.7 0.0
20 292 75 0.197 7.4 0.8 4.4 0.0 -87.8 0.0
25 290 74 0.247 11.6 1.9 3.8 0.0 -61.5 0.0
30 289 73 0.297 16.8 3.2 2.3 0.0 -31.3 0.0
35 287 72 0.347 22.9 4.7 -0.1 0.0 1.1 0.0
40 285 71 0.397 29.9 6.6 -3.5 0.0 35.0 0.0
45 283 70 0.448 38.0 8.6 -7.9 0.0 69.8 0.0
50 281 69 0.498 46.9 11.0 -13.2 0.0 105.3 0.0

 

Damn man you are putting in a lot more math into killing deer than I.

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your off in weeds. You can’t shoot well enough to use that kind of data

 

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ASctuall

Actually I can. Dime size groups at 20-30 yards. I have to shoot at different dots to avoid destroying arrows. That is how you collect bucks. I apologize if this is a foreign concept to anyone.

I never occurred to me that some day I might need to justify knowing where my arrow is going. But, here we are

See the attached screen cap of the txt file, a newer bow slinging shafts at 420 ft/s.

I think the image will render better than the copypasta I experimented with previously.

Forget the decimals. They happen to be spot on, but the way I use this data set is to know that from zero to about 40 yards I really don't need to worry about drop/trajectory. One pin covers all that range. Sure, if you had all day and precise knowledge of the distance you could make a slight adjustment. I don't want that in my head when time matters.

The import part is what happens at 45, 50, 55 and 60?

The answer is simple to keep in your head: 3 low, 6 low, 9 low and 12.

One could burn up a bow string to determine all this on targets of varying distance, with accuracy and group size influencing the results. This is the elegant solution.

Are we all on the same page now?

 

yeah Dime size groups at 30. your playing with more than the numbers buddy.

 

Wut?

 

Well boys looks like we have a fun new troll to enjoy. It's been a few years. Who was the last guy again.... Man it was great...... Tigger i think

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Well gee. I been doing it wrong this whole time.

 

Apparently you are calling me a liar despite your having zero information to back your accusation? Unless you meant 'playing' with the bow. Tuning it up in many ways. Tuning is key to accuracy/consistency.

And you follow him up with calling me a troll?

I'm pretty sure neither of you knows much of anything about me. Except that you apparently don't like me already

I'll decline this opportunity to engage is a pissing match. ... moving right along ...

 

Let's see this rig you use that you use all these mathematics on.

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Dime sized groups at 30 is world champion olympic level shooting, just saying.

 

I'm a firm believer in the KISS concept. You are familiar with that, right?