Elevation, MOA, Air Pressure POI, WTF

peacefrog said:
Does this happen to anyone else? I know there are variables and differences between ballistics programs, I was at the range today and plugged in my variables into iSnipe to get some dope. I was shooting at 300 yards, and iSnipe gave me an elevation to dial in of 2.8 MOA. In reality, I needed 4.5 MOA on the scope to hit centre of target today. This is not the only instance of iSnipe being off, or different than reality. My first shots with 2.8 MOA on the scope hit about 5-6" low, centred but low. When I dialed up to 4.5 MOA it was dead on centre 3 shots that could be covered with a .75" patch, very little wind today, sunny about 8 Celsius.

Earlier this year, I was running at most 3.5 MOA to 300, and one day in July, only 1.5 MOA was required.

Nothing with my load has changed. 39.2 gr of Varget pushing a 129 gr VLD out of a 30" match barrel chambered in .260 Remington. My velocities today were in line exactly with earlier data and I'm averaging 2906 fps.

If I understand correctly Varget is supposed to be temp stable, no?

So is it air pressure, temperature?? I'm lost now. I keep everything as consistent as possible and try to make perfect shots every time I pull the trigger. Everything is tight (scopes, bases, rings, action screws). So looking for some wisdom here. Thanks.
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You claim you went from 1.5 moa come up at 300, to 3.5 moa come up at 300 during the year. This is not going to balance anywhere in any ballistic program, you have gear related problems period.
 
Canuck525 said:
There is something wrong here. There is no way on earth it would change from 1.5 to 4.5 moa at 300 .It wouldn't even have a 3 moa change at 1000 yards. It's either your scope( is the paralex correct as well), shooting form or it's even possible the change in temperature may be affecting the bedding . It could also be possible that your muzzle heavy causing changes or stress on the action or not placing the bags the same .

The only other possible explanation is if you are shooting in a gravel pit. You can get significant up thermals in the summer and down drafts in cold temperatures but I have never seen a 3 moa change for this.
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I can't explain it. Our range is long and narrow, maybe thermal, air temp and humidity do weird stuff I don't know about on the range. The thought of muzzle heavy has crossed my mind, perhaps it's too much stress on the action... I have a hack saw around here somewhere...

now where was that...
 
Canuck525 said:
Personally, I think it is a bedding issue which is changing in variable temps/humidity
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Bedded professionally in a XLR chassis. I think it's some kind of sorcery, or witchcraft. :stirthepot2:

Honestly the more I think about it, I'm leaning towards something like to much stress on the action, maybe some weird harmonics happening from having a 30" barrel hanging off it. Seriously considering radical surgery and having 4-6" lopped off and see if that changes things.
 
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