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Accuracy change with Altitude change.

 
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  #1  
Old 11-13-2012, 07:53 PM
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Join Date: Dec 2010
Location: Fairview Alfa, Louisiana
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Accuracy change with Altitude change.

Fellas , my home address is at around 200 feet above sea level in louisiana where I worked up the hunting load for a elk hunting trip in Colorado where elevation was adout 9500'. Accuracy was averaging 3/4" @ 100yds. After rangeing testing the load out to 600 yards and adjusting the numbers for altitude and average temperature range I felt I was ready to go !! . After arriving for the hunt I went to the local dump/ shooting range where I shot a group that measured a little over an inch , so I shot another and it was just about and inch. After checking every thing I could not find a thing loose . After returning home I check the zero and after a cleaning the rifle shoots at its previous 3/4" grouping . The rifle was clean when shot in Colorado. I shot both sets of groups from my portable bench whitch I took with me . I am at a lose here , Is it possible for a load to be affected in terms of acccuracy aside from trajectory due to altitude and or temperature? thanks PC401
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Old 11-15-2012, 12:25 AM
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Location: Huron, SD
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Re: Accuracy change with Altitude change.

A 1/4" deviation in accuracy is not something that is easy to identify. Point in fact, I've only met 2 people in my entire life that were consistent 1/4 moa shooters.

Having an "off day" can cause much more than that. Going from 200ft to over 9,000ft is known to put someone "off" pretty damn easily.
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Old 11-15-2012, 12:50 AM
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Re: Accuracy change with Altitude change.

It could even be from you breathing heavier in the thinner air.
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Old 11-15-2012, 09:36 AM
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Join Date: Oct 2007
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Re: Accuracy change with Altitude change.

I agree....altitude would have no effect on accuracy. Your accuracy will change if you change the INTERIOR BALISTICS, not the EXTERIOR BALISTICS.

Tod
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Old 11-15-2012, 06:17 PM
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Join Date: Dec 2010
Location: Fairview Alfa, Louisiana
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Re: Accuracy change with Altitude change.

Well fellas , I think that it could be just me as well, I suppose that the stress of wanting to maintain accuracy while on a serious hunting could shew my normal shooting ability. I appreciate your thoughts! pc401
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  #6  
Old 11-16-2012, 12:39 AM
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Join Date: Nov 2012
Location: St Anthony ID
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Re: Accuracy change with Altitude change.

Tempture, humidity, altitude,(barometric pressure) will all affect group size 1/4 in change in size is well within the norm. Some powders are much more temp sensitive and velocity change can be significant witch will affect accracy.
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  #7  
Old 11-16-2012, 01:52 PM
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Re: Accuracy change with Altitude change.

Quote:
Originally Posted by BPreheim View Post
Tempture, humidity, altitude,(barometric pressure) will all affect group size 1/4 in change in size is well within the norm. Some powders are much more temp sensitive and velocity change can be significant witch will affect accracy.
Hogwash!!! You are talking about interior balistics. If the velosity is the same, the group size is the same. You are talking about reducing/increasing velocity due to temp sensitivity of the powder. the only thing that does that is INTERIOR balistics. Change the velosity and of course the group size could get bigger....but..it could also get SMALLER. It just depends on how carefull and anal you were during load development. Baro, altitude, humidity have ZERO affect on accuracy. Temp also has zero effect on accuracy, provided that you either keep your ammo the same temp as your load development or you tweek your velosity to keep it constant with your load development.
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