Long Range Hunting Online Magazine


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

Rifles, Bullets, Barrels & Ballistics Applied Ballistics


Reply

Up/Downhill corrections

 
LinkBack Thread Tools Display Modes
  #15  
Old 06-07-2007, 11:15 AM
Sponsor
 
Join Date: Jun 2007
Location: North Idaho
Posts: 1,841
Re: Up/Downhill corrections

Devin,

I have and have used all 3 NF/Exbal versions (palm, Pocket PC, desktop) the pocket PC is the way to go, however you need the desk top version to print a backup drop sheet to keep with your PC for when it doesn't work.
__________________
Shawn Carlock

www.defensiveedge.net
1-208-687-2659
Reply With Quote
  #16  
Old 06-07-2007, 11:21 AM
Sponsor
 
Join Date: Jun 2007
Location: North Idaho
Posts: 1,841
Re: Up/Downhill corrections

Edge,

I have not used the SMI lab and can only speak of the Exbal program for this iinfo. If you apply cosi ne to distance, cosine to dope for the actual yardage, and run it through Exbal program you will in fact get 3 different answers. I physiclly shot 4 different rifles on a given # of shots at different angles and distances and compared my results with the 3 corrections. The Exbl program was never more the .25 moa off from my actual field dope for the shot. I don't know if you program runs applied cosine directly or through a formula like the Exbal.
__________________
Shawn Carlock

www.defensiveedge.net
1-208-687-2659
Reply With Quote
  #17  
Old 06-07-2007, 11:37 AM
Silver Member
 
Join Date: Mar 2006
Posts: 161
Re: Up/Downhill corrections

Thanks Shawn. I guess I'm going to have to save my pennies for a PocketPC now. [img]/ubbthreads/images/graemlins/grin.gif[/img]

I just ran a little experiment on my calculator and even if you take that actual cosine of 45 (.707106781) and then multiply it by your 800 yard dope you still get 18.738 MOA. So the NF/Exbal program must take into account all the environmental factors also, which would otherwise take a person a long time to figure out by simply using a calculator.

Devin
Reply With Quote
  #18  
Old 06-07-2007, 12:53 PM
Gold Member
 
Join Date: Sep 2003
Location: Blighty
Posts: 638
Re: Up/Downhill corrections

I typed this one or 2 year's ago on PLRH; I'm too idle to type it again [img]/ubbthreads/images/graemlins/smile.gif[/img] looks like noone read it anyway!

<font color="blue"> The 'base line' [or 'corrected horizontal range' or 'magic physical-law defying range'] method, although used by many is actually the least accurate way of using your cos measurement...because it has absolutely nothing to do with the ballistics of what's going on in inclined fire!

Far more accurate is to multiply the comeup you would have applied for your laser distance by the cos of the angle.
This does reflect what is going on ballistically ...the bullet has the same TOF to a given target regardless of angle of fire...it therefore drops the same amount regardless of angle of fire (it doesn't magically drop less!)

...what changes is your perspective to that drop (and therefore the apparent shape of the trajectory).

Hold a pencil vertically in your hand at arms length (with your arm horizontal); lets say the pencil length represents your bullet drop at 1 arms length.

Now drop your arm to 45deg, but keep the pencil vertical.

The pencil appears shorter, even though it has remained the same length

....ie the drop has remained the same, but less drop is apparent because of your perspective.

How long does it appear to be? multiply it's actual length by the cos of 45deg...just the same as multiplying your laser range comeup by the cos of the angle!

You'll see that Ward at ACI has recently amended his instructions for the ACI to reflect this.

Here's a link to a link on the ACI site where all this is explained by one of the Sierra Infinity software designers:

http://www.snipertools.com/article4.htm

Only read this bit if you're a ballistics nerd: The software engineer concludes that a set of rather complicated calculations based on actual bullet drop (rather than simply comeups) are somehow yet more accurate again (this is the method he uses in the Sierra program)...he tests his theory by comparing the results of this type of calculation against his Sierra outputs...they are close to each other so he concludes greater accuracy...what he fails to point out / realise is that both the calculation method and his software method are the same...of course they'll be close!! ...nothing proved!

...unless a ballistic prog goes into a full vector analysis of how gravitational acceleration is affecting bullet velocity throughout its time of flight (and therefore calculating the minute changes to TOF at varying angles of projection)(ie 'straight up' it will directly slow the bullet, 'straight down will speed it)the only greater accuracy from a basic ballistic prog comes from the fact that 'comeups' represent data that has been rounded-of to the nearest click value, if you use that and then round-off the result..the answer will be slightly less accurate than precise raw data that has only been rounded off once.
</font>


...and as a common-sense check:

Artillerymen receive target locations as grid references.

Grid references alone provide no angle of sight data (ie should the target happen to be on top of a hill or in a valley); and so Gunners are presented immediately with what some riflemen are calling 'true horizontal range'.

But Gunners, if working manually, will use this distance, (plus some trig based on the calculated angle of sight between their location and the target's) to work out the 'slant range' to the target (and then do some other mumbo jumbo too)

....the point being; true long range Jedi [img]/ubbthreads/images/graemlins/smile.gif[/img] do (and have done since WW1!) the exact opposite of what the 'corrected horizontal range' riflemen suggest.
Reply With Quote
  #19  
Old 06-07-2007, 01:08 PM
Silver Member
 
Join Date: Sep 2006
Location: Nebraska
Posts: 211
Re: Up/Downhill corrections

sorry Shawn,

please read the last line for explaination of what happened. Your 100% right on the &lt;.99 COS, should have thought about the answer more.
Reply With Quote
  #20  
Old 06-07-2007, 01:54 PM
Platinum Member
 
Join Date: Jun 2001
Location: Potomac River
Posts: 5,059
Re: Up/Downhill corrections

[ QUOTE ]
looks like noone read it anyway!


[/ QUOTE ]

Just call me "Noone" from now on. [img]/ubbthreads/images/graemlins/grin.gif[/img]
__________________
The Smokin Fur Rifle Club
Reply With Quote
  #21  
Old 06-07-2007, 02:30 PM
Gold Member
 
Join Date: Sep 2003
Location: Blighty
Posts: 638
Re: Up/Downhill corrections

aaagh! [img]/ubbthreads/images/graemlins/grin.gif[/img]
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes


Similar Threads for: Up/Downhill corrections
Thread Thread Starter Forum Replies Last Post
The Saga Of The Uphill-Downhill Shot, Part I ADMIN Technical Articles - Discussion 12 05-12-2012 10:55 AM
uphill/downhill shooting questions rocknwell The Basics, Starting Out 12 07-11-2011 05:54 AM
Shooting uphill vs downhill lefty15 Long Range Hunting & Shooting 10 10-09-2009 01:13 PM
Windage Corrections MOA Yakblast Rifles, Bullets, Barrels & Ballistics 2 03-31-2009 08:15 PM
Do I need to worry about shooting downhill angles? sambo3006 Rifles, Bullets, Barrels & Ballistics 4 06-26-2008 09:00 PM


All times are GMT -5. The time now is 10:25 AM.


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