Long Range Hunting Online Magazine


Go Back   Long Range Hunting Online Magazine > Rifles, Reloading, Optics, Equipment > Rifles, Bullets, Barrels and Ballistics


Reply

BEWARE, Problems with Exbal and G7 BC's

 
LinkBack Thread Tools Display Modes
  #15  
Old 12-11-2010, 09:41 PM
Bronze Member
 
Join Date: May 2006
Posts: 53
Re: BEWARE, Problems with Exbal and G7 BC's

Bigngreen,
I shoot this rifle all the time but 1000 yards is quite a ways for a 223 AR15! On a side note, it is a Les Baer super varmint and it is amazingly accurate! I will shoot it in the 600-700 yard range quite a bit. As I said before, the 1000 yard drop number was more for comparison. The actual range isn't overly important from a comparison point of view. Or said another way, there were significant errors at shorter distances as well.

Bryan,
I have to laugh at the comment your collegue made. Just the other day while troubleshooting a difficult problem at work, a very experienced senior engineering collegue of mine made the same comment---"It's either that....or something else"--good stuff! Engineers are all very similar creatures!
Reply With Quote

  #16  
Old 12-11-2010, 10:00 PM
Bronze Member
 
Join Date: May 2006
Posts: 53
Re: BEWARE, Problems with Exbal and G7 BC's

It is very interesting to me that Bigngreen is getting very similiar results with Loadbase as I am getting with the "upgraded" version of Exbal. I do not have Loadbase but it seems like some of the programs are calculating drops of around 430" and some of the programs are calculating drops of around 447" at 1000 yards. The questions is: Which one is correct? I am not sure at this point. Perhaps it has to do with the atmospheric standards as Bryan mentioned (ASM vs ICAO)?
Reply With Quote
  #17  
Old 12-11-2010, 10:11 PM
Platinum Member
 
Join Date: Nov 2008
Location: SW Montana
Posts: 4,503
Re: BEWARE, Problems with Exbal and G7 BC's

Thanks, my only interest is because you gave such good complete data compared to most and since I don't do all the engineering thing I have to hack a good correction out of trial and error so the more trajectories a guy can run the better you get with the tools at your disposal, not trying to crash out you thread.

What is of interest to me is the last few hundred feet per second before going transonic, LB is within a few inches all the way with Berger and JBM, didn't check my Exbal cause all I use is the PPC version, till you get into the farthest end of the trajectory. So far in my shooting near the transonic Exbal, Berger, JBM will all be about 2 MOA low, LB will be really close. My interest is not specifically any is better than the other but how to make each one function correctly out to max range. I will be adding Shooter at my next phone up grade, I lack the engineering but love muddling my way through it.

Nice thread, picked up a few things. Brian if Exbal is using ASM should I convert the BC from ICAO to ASM for a more accurate correction in Exbal?
__________________
High Fence, Low Fence, Stuck in the Fence, if I can Tag it and Eat it, it's Hunting!

"Pain is weakness leaving your body"
Reply With Quote
  #18  
Old 12-11-2010, 10:16 PM
Platinum Member
 
Join Date: Nov 2008
Location: SW Montana
Posts: 4,503
Re: BEWARE, Problems with Exbal and G7 BC's

Quote:
Originally Posted by ericpetritz View Post
It is very interesting to me that Bigngreen is getting very similiar results with Loadbase as I am getting with the "upgraded" version of Exbal. I do not have Loadbase but it seems like some of the programs are calculating drops of around 430" and some of the programs are calculating drops of around 447" at 1000 yards. The questions is: Which one is correct? I am not sure at this point. Perhaps it has to do with the atmospheric standards as Bryan mentioned (ASM vs ICAO)?
I was also intrigued when I saw that, LB is ICAO but I can use it to convert to ASM to input a value to Exbal in ASM, I'll charge my PPC up and see what that changes.
I enjoy shooting the solution, sometimes it's back to the drawing board but like I said earlier I can not apply the engineering to a problem, I'm wired for hands on problem solving!

I converted the ICAO BC of .19 to a ASM BC of .187 and it made an 8in difference at 1000yrds in LB, definitely something to watch and makes me think I need to do some work with Exbal and may explain some of the error that I've been tweaking out with velocity changes that should be a BC change.
__________________
High Fence, Low Fence, Stuck in the Fence, if I can Tag it and Eat it, it's Hunting!

"Pain is weakness leaving your body"

Last edited by bigngreen; 12-11-2010 at 11:11 PM. Reason: more data
Reply With Quote
  #19  
Old 12-12-2010, 10:48 AM
Platinum Member
 
Join Date: Aug 2003
Location: NC, oceanfront
Posts: 3,301
Re: BEWARE, Problems with Exbal and G7 BC's

I believe ICAO + 78%RH = standard artillery atmosphere (SAA)
Pejsa was stuck on this oddity for quite a while, and Gerald may be borrowing from Pejsa's math for his solutions.
Personally, I convert all to ICAO. I could post a spreadsheet to do this for you if needed.
One thing I notice with this discussion though,, you keep referring to altitude. You already measure & hold station pressure, so there is never any reason to consider altitude.
DO NOT ENTER ALTITUDE
Reply With Quote
  #20  
Old 12-12-2010, 11:00 AM
SPONSOR
 
Join Date: Mar 2007
Posts: 521
Re: BEWARE, Problems with Exbal and G7 BC's

Quote:
Originally Posted by Mikecr View Post
You already measure & hold station pressure, so there is never any reason to consider altitude.
DO NOT ENTER ALTITUDE
Good point Mike.

Regarding Loadbase which uses Pejsa equations...

As I recall, the math used in the Pejsa equations defines drag as a function of velocity, not Mach number. This practice fails to capture the effects of temperature on Mach number and drag, which is real. The error would have the effect of predicting too much drop in low temperature.

The extra high drop predicted by Gerald's latest exbal suggest that he locked down the definition of speed of sound to the standard value, and removed the temperature dependence. 447" is excessive.

Quote:
Nice thread, picked up a few things. Brian if Exbal is using ASM should I convert the BC from ICAO to ASM for a more accurate correction in Exbal?
You can, by multiplying the ICAO BC by 1.018. Again, I'm assuming that exbal is using ASM. Careful with assumptions.

Interesting that exbal uses 29.92", 59 deg and 78% hum. Seems like a mixture of ASM and ICAO? I never heard of SAA, but it's a possibility that may explain why 1.8% doesn't exactly make up the difference.

-Bryan
__________________
Bryan Litz
Ballistician

Author of: Applied Ballistics for Long Range Shooting
And: Accuracy and Precision for Long Range Shooting

Reply With Quote
  #21  
Old 12-12-2010, 11:27 AM
Platinum Member
 
Join Date: Nov 2008
Location: SW Montana
Posts: 4,503
Re: BEWARE, Problems with Exbal and G7 BC's

Thanks for the reply Bryan! I try to dig into the underlying stuff but it can be messy!

So we have three standards out there ICAO, ASM and SAA?
__________________
High Fence, Low Fence, Stuck in the Fence, if I can Tag it and Eat it, it's Hunting!

"Pain is weakness leaving your body"
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes


Similar Threads for: BEWARE, Problems with Exbal and G7 BC's
Thread Thread Starter Forum Replies Last Post
Montana Wolves Beware MT4XFore General Discussion 4 08-16-2011 08:58 PM
BUYERS BEWARE Ballistic64 Long Range Scopes and Other Optics 11 11-20-2009 09:59 AM
Exbal problems Topshot Long Range Hunting & Shooting 5 02-22-2009 09:51 PM
Grandma went and did it now, whitetails beware! Ridge Runner Deer Hunting 10 12-21-2008 07:45 AM
Groundhogs beware! Ridge Runner Equipment Discussions 15 01-07-2007 02:07 PM


All times are GMT -5. The time now is 11:20 AM.


Powered by vBulletin ©2000 - 2014, Jelsoft Enterprises Ltd.
Content Management Powered by vBadvanced CMPS
All content ©2010-2014 Long Range Hunting, LLC