Long Range Hunting Online Magazine


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


Reply

Confusing Exbal Question

 
LinkBack Thread Tools Display Modes
  #1  
Old 12-28-2008, 12:12 PM
Gold Member
 
Join Date: Feb 2008
Location: Sonoma County, CA
Posts: 824
Confusing Exbal Question

I am using version 8.10 of the Nightforce Exbal program and shooting a 300 Win Mag at 3000 fps with a 180 gr. Accubond.

Elevation= 800 ft.
Temp= 50
RH= 50
Sight in distance= 200 yds.
I am using standard atmosphere pressure


At 675 yds it calls for 12.50 minutes.
At 1025 yds it calls for 27.25 minutes.

When shooting at the 675 yd target I am 3-4" high. When shooting at the 1025 yd target I am roughly 24" low and needed to correct the elevation to 31.00 minutes by trial and error. I tried to validate the trajectory at 675 with + 4" but then it calls for an even lower (26.00) elevation at 1025 yds. If I validate the trajectory at 1000 yds and say I am 24" low, it gives me a 29.75 elevation at 1025 which is closer but then the elevation for 675 is 13.75 which would even be higher. I am a little confused and not sure what would be the right thing to do to get both ranges right. What do you think?
Reply With Quote

  #2  
Old 12-28-2008, 12:24 PM
Silver Member
 
Join Date: Dec 2007
Posts: 322
Re: Confusing Exbal Question

I would go out and shoot from as many different distances as possible(100 yd. incraments would be best),and record the actual drop without adjusting your scope.Then adjust the b.c. on your Exbal program until the drop chart matches your actual results.I alway's seem to have to play around B.C. #'s to get things to match up with actual field testing.
Reply With Quote
  #3  
Old 12-28-2008, 12:30 PM
Platinum Member
 
Join Date: Oct 2005
Location: Michigan
Posts: 2,232
Re: Confusing Exbal Question

My guess would be that you're sight in distance is a little longer and your velocity is a little slower. Where did you get the velocity?

What type of group are you shooting at 200yds? Just a little bit high can really affect your 'actual' sightin distance in Exbal.

For example, 2850fps and a sight in distance of 255, puts your 675 at 13 MOA and your 1025 at 2950. This would be a pretty close match to the drops you listed in your posting.

Also, have you set your scope height exactly?

AJ
__________________
If some is good and more is better, then too much is just right.


My mind is a raging torrent, flooded with rivulets of thought, cascading into a waterfall of creative alternatives

Last edited by AJ Peacock; 12-28-2008 at 12:32 PM. Reason: Further explanation
Reply With Quote
  #4  
Old 12-28-2008, 12:58 PM
Gold Member
 
Join Date: Feb 2008
Location: Sonoma County, CA
Posts: 824
Re: Confusing Exbal Question

I set my scope height at 1.6" That should be pretty much on the money.

My sight in at 200 was only about 1/4" high.

The loads were chronographed with two units. But, there may be some flaw to this. I have an old Pact that shows 2890 fps, but this same load used to show 3000 fps. All components were the same, even the number of firings for the brass, same lot # of all other components. I used a friends Chrony and it showed 3016 fps. I thought 3000 would be very close to actual.

When I validate for 675 yds, the velocity changes to 3044 fps. When I validate for 1000 yds, the velocity changes to 2887 fps.
Reply With Quote
  #5  
Old 12-28-2008, 01:15 PM
Gold Member
 
Join Date: Feb 2008
Location: Sonoma County, CA
Posts: 824
Re: Confusing Exbal Question

AJ, I just ran some of the numbers you were talking about through the program and see what you mean. A little here and there changes things. I am going to go back to the range and rework this from scratch.

Should I expect Exbal to be accurate at all of these ranges if the input is accurate?
Reply With Quote
  #6  
Old 12-28-2008, 01:21 PM
Platinum Member
 
Join Date: Oct 2005
Location: Michigan
Posts: 2,232
Re: Confusing Exbal Question

Quote:
Originally Posted by Moman View Post
AJ, I just ran some of the numbers you were talking about through the program and see what you mean. A little here and there changes things. I am going to go back to the range and rework this from scratch.

Should I expect Exbal to be accurate at all of these ranges if the input is accurate?
I've found Exbal to be very accurate when you get the inputs correct. The first thing is to get your velocity as close as possible. I have a CHRONY and it is always WAY to high. My CED M2 velocities have always made my Exbal estimates very close.

AJ
__________________
If some is good and more is better, then too much is just right.


My mind is a raging torrent, flooded with rivulets of thought, cascading into a waterfall of creative alternatives
Reply With Quote
  #7  
Old 12-28-2008, 01:30 PM
Silver Member
 
Join Date: Dec 2006
Posts: 308
Re: Confusing Exbal Question

I guess the next thing to check is your scope. Get your rifle on a dead rest at the range and have someone dial up your scope. Make sure it is tracking correctly. 1.047" per 1 moa. After about 21 moa the .047 extra adds up to another inch. I would see if that is the case with your scope.

Box test would be a good thing to do as well.
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes


Similar Threads for: Confusing Exbal Question
Thread Thread Starter Forum Replies Last Post
Exbal question royinidaho Equipment Discussions 14 09-11-2009 08:47 PM
exbal question flims Long Range Hunting & Shooting 3 12-15-2008 04:34 AM
Exbal question Midgetsniper Long Range Hunting & Shooting 0 07-26-2008 12:12 AM
Exbal Question...... Sendero_Man Long Range Hunting & Shooting 6 07-01-2007 10:59 AM
Another Exbal question Rifles, Bullets, Barrels and Ballistics 2 06-01-2005 06:52 AM


All times are GMT -5. The time now is 09:14 AM.


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