HuntingNut
HuntingNut
   Login or Register
HomeCommunity ForumsPhoto AlbumsRegister
     
 

User Info

Welcome Anonymous


Membership:
Latest: Yt_Nelson
New Today: 0
New Yesterday: 0
Overall: 12383

People Online:
Members: 0
Visitors: 186
BOT: 4
Total: 190
Who Is Where:
 Visitors:
01: Statistics
02: Photo Albums
03: Photo Albums
04: Photo Albums
05: Forums
06: Forums
07: Photo Albums
08: Photo Albums
09: Forums
10: Forums
11: Forums
12: Forums
13: Photo Albums
14: Forums
15: Photo Albums
16: Forums
17: Forums
18: Your Account
19: Forums
20: Forums
21: Forums
22: Forums
23: Photo Albums
24: Forums
25: Forums
26: Forums
27: Forums
28: Statistics
29: Photo Albums
30: Forums
31: Forums
32: Forums
33: Forums
34: Photo Albums
35: Forums
36: Photo Albums
37: Photo Albums
38: Forums
39: Forums
40: Forums
41: Your Account
42: Home
43: Forums
44: Forums
45: Forums
46: Your Account
47: Forums
48: Your Account
49: Forums
50: Forums
51: Forums
52: Photo Albums
53: Forums
54: Forums
55: Forums
56: Forums
57: Forums
58: Forums
59: Forums
60: Your Account
61: Forums
62: Photo Albums
63: Photo Albums
64: Forums
65: Forums
66: Forums
67: Forums
68: Photo Albums
69: Forums
70: Your Account
71: Forums
72: Forums
73: Forums
74: Photo Albums
75: Forums
76: Forums
77: Forums
78: Forums
79: Forums
80: Forums
81: Forums
82: Forums
83: Forums
84: Forums
85: Photo Albums
86: Forums
87: Forums
88: Forums
89: Forums
90: Forums
91: Photo Albums
92: Home
93: Photo Albums
94: Forums
95: Photo Albums
96: Home
97: Forums
98: Forums
99: Forums
100: Forums
101: Forums
102: Photo Albums
103: Forums
104: Forums
105: Forums
106: Photo Albums
107: PointBlank Ballistics
108: Forums
109: Forums
110: Forums
111: Forums
112: Forums
113: Forums
114: Photo Albums
115: Forums
116: Photo Albums
117: Forums
118: Forums
119: Forums
120: Forums
121: Photo Albums
122: Forums
123: Your Account
124: Forums
125: Forums
126: Photo Albums
127: Forums
128: Photo Albums
129: Forums
130: Forums
131: Home
132: Photo Albums
133: Photo Albums
134: Photo Albums
135: Forums
136: Forums
137: Photo Albums
138: Forums
139: Forums
140: Forums
141: Forums
142: Forums
143: Forums
144: Forums
145: Forums
146: Forums
147: Forums
148: Forums
149: Forums
150: Forums
151: Forums
152: Forums
153: Photo Albums
154: Forums
155: Forums
156: Forums
157: Forums
158: Photo Albums
159: Forums
160: Forums
161: Forums
162: Forums
163: Forums
164: Forums
165: Forums
166: Forums
167: Forums
168: Forums
169: Forums
170: Forums
171: Photo Albums
172: Forums
173: Forums
174: Photo Albums
175: Forums
176: Forums
177: Your Account
178: News
179: Photo Albums
180: Forums
181: Forums
182: Forums
183: Your Account
184: Forums
185: Forums
186: Forums
  BOT:
01: Forums
02: Forums
03: Forums
04: Forums

Staff Online:

No staff members are online!
 

Coppermine Stats
Photo Albums
 Albums: 312
 Pictures: 2417
  · Views: 250282
  · Votes: 1255
  · Comments: 86
 

Support our Advertisers

Determining ballistic coefficient...
Help / Support / How-to's / Discussion related to PointBlank Software and External Ballistics in general
Go to page 1, 2  Next
Post new topic   Reply to topic   Printer Friendly Page    Forum Index » PointBlank Software

View previous topic :: View next topic  
Author Message
kudukid
Rookie Member
Rookie Member


Joined: Nov 21, 2011
Posts: 3

PostPosted: Mon Nov 21, 2011 8:22 am    Post subject: Determining ballistic coefficient... Reply with quote

Can PointBlank compute ballistic coefficients given data from muzzle and downrange chronograph recorded speeds?

I am skeptical that this is being done at the various bullet manufacturers facilities.
Back to top
View user's profile
Ominivision1
Super Member
Super Member


Joined: Sep 20, 2010
Posts: 2985
Location: Iowa

PostPosted: Mon Nov 21, 2011 11:47 am    Post subject: Re: Determining ballistic coefficient... Reply with quote

I have never tried what you are describing but Dallan will be along to give you a heads up on your question.

I also take the bullet coefficients from the manufacturers with a grain of salt so I use this calculator.

www.tmtpages.com/calcb...calculator

_________________
Regards

Limitations are but boundaries created inside our minds.
Back to top
View user's profile Photo Gallery
DallanC
Site Admin
Site Admin


Joined: Jan 18, 2005
Posts: 3082
Location: Utah

PostPosted: Mon Nov 21, 2011 12:23 pm    Post subject: Re: Determining ballistic coefficient... Reply with quote

kudukid wrote:
Can PointBlank compute ballistic coefficients given data from muzzle and downrange chronograph recorded speeds?

I am skeptical that this is being done at the various bullet manufacturers facilities.

Yes. PointBlank will compute this if you know muzzle and 100 yard velocities. It basically runs the computations over and over internally adjusting the BC until it finds the closest match to the velocites given. Its pretty accurate.


-DallanC
Back to top
View user's profile Photo Gallery
kudukid
Rookie Member
Rookie Member


Joined: Nov 21, 2011
Posts: 3

PostPosted: Mon Nov 21, 2011 1:48 pm    Post subject: Re: Determining ballistic coefficient... Reply with quote

Thanks...any idea where to look for this in the program and how to apply it? I'm new to PointBlank.

DO'C
Back to top
View user's profile
Fireman_DJ
Member
Member


Joined: Aug 11, 2011
Posts: 104
Location: Victoria, Australia

PostPosted: Mon Nov 21, 2011 4:49 pm    Post subject: Re: Determining ballistic coefficient... Reply with quote

At the top, hit Ballistics. Then on the bottom tabs hit Misc. Then it's the first button.

Note, it says to use the muzzle and 100 meter velocities. on the screen, but when you click the button it'll tell you either yards or meters depending on your unit of measurement settings.
Back to top
View user's profile
kudukid
Rookie Member
Rookie Member


Joined: Nov 21, 2011
Posts: 3

PostPosted: Mon Nov 21, 2011 9:41 pm    Post subject: Re: Determining ballistic coefficient... Reply with quote

Many thanks - should have second Chrony here on Thanksgiving day.
Don
Back to top
View user's profile
Fireman_DJ
Member
Member


Joined: Aug 11, 2011
Posts: 104
Location: Victoria, Australia

PostPosted: Mon Nov 21, 2011 10:15 pm    Post subject: Re: Determining ballistic coefficient... Reply with quote

Why two chronys? They might read differently anyway.

I assume you're hand-loading, so make sure you load a very precise batch (weight every charge of powder), then fire 10 shots with the chrony at the muzzle. Get the average value, then move the chrony and repeat at 100 yards/meters.

Take the two average values and plug them into PB.

It'll give a more accurate reading for the BATCH of pills your trying. Some may have a slightly better BC then others in the same batch.

Averages are your friend.
Back to top
View user's profile
SyberShooter
Member
Member


Joined: Jul 23, 2010
Posts: 93
Location: Arizona

PostPosted: Tue Nov 29, 2011 8:57 am    Post subject: Re: Determining ballistic coefficient... Reply with quote

.... as are standard deviations
Back to top
View user's profile
Ghost
Member
Member


Joined: Nov 20, 2011
Posts: 25
Location: European Forrest

PostPosted: Tue Nov 29, 2011 11:01 am    Post subject: Re: Determining ballistic coefficient... Reply with quote

If not know the 100yds velocity, what then? Cause can't let the program calculate something if not can fill in the BC. And only can find out the 100velocity after that. So?? Confused
Back to top
View user's profile Visit poster's website
Ominivision1
Super Member
Super Member


Joined: Sep 20, 2010
Posts: 2985
Location: Iowa

PostPosted: Tue Nov 29, 2011 11:37 am    Post subject: Re: Determining ballistic coefficient... Reply with quote

Ghost wrote:
If not know the 100yds velocity, what then? Cause can't let the program calculate something if not can fill in the BC. And only can find out the 100velocity after that. So?? Confused

If you don't have access to a chrony, click the link on my post above and enter the data, at the top, the left side is for cast bullets and the right side is for jacketed bullets. Select what kind of bullet you have in the appropriate columns and enter data in the boxes and it will calculate (approx) BC's of given bullets.

_________________
Regards

Limitations are but boundaries created inside our minds.
Back to top
View user's profile Photo Gallery
Ghost
Member
Member


Joined: Nov 20, 2011
Posts: 25
Location: European Forrest

PostPosted: Tue Nov 29, 2011 4:47 pm    Post subject: Re: Determining ballistic coefficient... Reply with quote

A nice one to use too. Thx Ominivision.


Ghost
Back to top
View user's profile Visit poster's website
slimjim
Super Member
Super Member


Joined: May 16, 2009
Posts: 6849
Location: Fort Worth TX

PostPosted: Tue Nov 29, 2011 10:05 pm    Post subject: Re: Determining ballistic coefficient... Reply with quote

From what I've read, velocity measurements at 100 yards for deriving bullet BC is not very accurate. It's more accurate if you use a velocity closer to 300 yards. I've done this a couple of times and you need an accurate rifle you have confidence in to shot at your chrony at that distance. Of course, if you rifle isn't accurate, having a good BC value is irrelavant.

You shouldn't need a special funciton to derive BC. Just enter the data into the trajectory/ballistic caluclater with your guess at BC. Then adjust the BC value until the velocity at the range you took the chrony at match. I did this last weekend for a Barnes .223 62gr TTSX. I quess a BC of .3 and adusted it down to .292 which is where the velocity I had at 250 yards matched.

_________________
"To anger a conservative, lie to him. To anger a liberal, tell him the truth." - Theodore Roosevelt

"The world is a dangerous place to live; not because of the people who are evil, but because of the people who don't do anything about it." - Albert Einstein
Back to top
View user's profile
chambered221
Super Member
Super Member


Joined: Aug 17, 2007
Posts: 3432
Location: Lost for good !!!

PostPosted: Wed Nov 30, 2011 8:48 am    Post subject: Re: Determining ballistic coefficient... Reply with quote

Some added important info when dealing with Ballistic Coefficients !!!

Ballistic Coefficient - A comparative number to judge one bullet to another as to it's ability to travel through air and retain velocity.

First and foremost, The manufactures published numbers are arrived at by means of a mathematical calculation. In other words they are a pencil and paper numbers that only hold true in a perfect world.
This is one of the reasons manufactures don't always list the info and why so many re-loaders don't trust the numbers.

One aspect that can explain this is stability. Simply shooting identical bullets through barrels with different twist rates can change the BC of a given bullet.
When a bullet leaves the muzzle it is at it's most unstable point. The amount of time it takes to stabilize the bullet will change the BC of the bullet.
So once again, as it so often happens in the world of re-loading, variables come into play (as you can imagine they are numerous) and changes things. These changes can be small and insignificant to most hunters but they can also have huge and dramatic results to long range shooters.

The muzzle velocity is an important aspect of BC. A bullet shot from a .308 Winchester will not have the same BC as an identical bullet shot from .300 Weatherby. This is because the lower starting velocity puts the bullet into a different operating parameter.

BC from identical bullets can also change, imperfections in the bullet, tip damage and air disturbances can also create changes. Keep in mind the most important aspect to determining BC is the Time Of Flight. Change TOF and BC changes with it.


This brings us to another important point. When determining BC by means of 2 chronographs it is imperative to know the exact distance ( needs to be measured ) between the two points. If the proper distance is not used in the calculation the BC will be incorrect due to the TOF calculations.
The 2 chronographs also need to read to about 1fps of one another. Set them up in a over lapping manner to determine consistency between the two. Again TOF calculations will be incorrect if there is too much variance.

_________________
Ask as many people needed, sooner or later your question will be answered the way you want it answered !!!

A free people ought not only to be armed and disciplined, but they should have sufficient arms and ammunition to maintain a status of independence from any who might attempt to abuse them, which would include their own government.
~George Washington
Back to top
View user's profile Photo Gallery
Ominivision1
Super Member
Super Member


Joined: Sep 20, 2010
Posts: 2985
Location: Iowa

PostPosted: Wed Nov 30, 2011 9:07 am    Post subject: Re: Determining ballistic coefficient... Reply with quote

Good point Chambered, further reading from Sierras website is HERE

_________________
Regards

Limitations are but boundaries created inside our minds.
Back to top
View user's profile Photo Gallery
chambered221
Super Member
Super Member


Joined: Aug 17, 2007
Posts: 3432
Location: Lost for good !!!

PostPosted: Wed Nov 30, 2011 11:27 am    Post subject: Re: Determining ballistic coefficient... Reply with quote

Excellent add on !!!

IMO Sierra has led the way with their BC research and listing of data.



Point #1 says it all !!! Sniper

Point #2 can be argumentative....... This is basically due to opposing sides not being on the same page. Here again the paper calculations don't deal with air resistance or air density. So on paper it's a constant as opposed to real word cause and effect.

_________________
Ask as many people needed, sooner or later your question will be answered the way you want it answered !!!

A free people ought not only to be armed and disciplined, but they should have sufficient arms and ammunition to maintain a status of independence from any who might attempt to abuse them, which would include their own government.
~George Washington
Back to top
View user's profile Photo Gallery
Display posts from previous:   
Post new topic   Reply to topic   Printer Friendly Page    Forum Index » PointBlank Software
Page 1 of 2
All times are GMT - 7 Hours
Go to page 1, 2  Next



Jump to:  


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum


Advertisements
 


Valid CSS! Valid HTML 4.01!
Click to check if this page is realy HTML 4.01 compliant for speed :)

All logos and trademarks in this site are property of HuntingNut.com.
The comments are property of their posters, all the rest © 2011 by HuntingNut.com
Interactive software released under GNU GPL, Code Credits, Privacy Policy

.: Upgraded to DragonFly 9.2 by Dizfunkshunal :.