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Mirage help...

 
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Old 07-21-2010, 10:17 AM
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Mirage help...

So, I've not learned much about mirage as I should've and without thinking through the potential issues of going to the range in the middle of the day in July to do some load development, I end up at the range with nasty mirage.

I'm only shooting at 200 doing a bit of load development using Jerry Teo's method outlined in an article here at lrh, which has worked well for me in the past. Letting barrel cool pretty well between groups of two, just trying to find pressure and some hint of accuracy working up in .5g increments. At any rate, I've got mirage going up (it appears--range is grass and it's about 65F in the shade with 7-8 o'clock wind variable 2-5 mph or so) it appears, then mirage going sideways, it appears. And, i'm lucky to hold 3/4 MOA and this rifle should be capable of way less than that.

I probably just should've packed up and gone home when I saw the mirage, I suppose. Did find pressure ceiling, so that was useful. Groups appeared to be 'clocking' a bit as Teo's article talks about--althought that is something to look for a little later in his process, but for the most part, the 2 shot groups were either pretty much verticle or horizontal, which makes me wonder if I was just seeing hor./vert. mirage issues. If so, I didn't realize how much effect the mirage would have at 200 yds.

Make any sense to anybody?
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Old 07-21-2010, 11:08 AM
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Re: Mirage help...

Mirage is heavily influenced by the temperature difference between the ground/ground cover and the air above it.

Pretty much like the visible waves when you look through a camp fire.

The worst time to shoot, they tell me, is when its boiling straight up. I think that statement is made because this condition is not usually a regularly repeatable condition.

I was conditioned during my light and heavy varmint bench rest shooting in the 70s. Mirage at the range was very excessive due to the bare soil. In fact, Ned Bench, the fella that had his near 0.000" group featured in one of the early Speer manuals, flew over to shoot with us. He was a great guy and we learned much from him. However, everyone out shot him that day. His comment was that the conditions caught he as bad as he's ever been caught.

You'll see the mirage wavering to the right then wavering to the left then just boiling straight up. Take a gun vise with you and set up on the target. Then just sit there an watch the POI hover around the reticle center. On a normal day day summer or winter I see at times over an inch at 200.

I get confused, kind of a condition, that I can't with confidence state that the apparent POI most "with" the mirage or "against" it. When I had this confusion on the line, I'd shoot a sighter. Then get pissed because I wasted a great shot.

Leave you big gun in the house and take a great shooting one, even a 22 lr if need be. Then go shoot. Shoot, and shoot and shoot. Paying attention to the conditions/mirage.

The angle of the mirage is proportional to wind velocity. Another important factor is wind direction. Mirage drift direction is easy to see. But with out wind direction you'll be missing part of the information.

When you catch on, you'll be more able to understand when you get busted by the conditions and have a few more grins than frowns. (Remembering there will always be frowns.)

Once, after a lot of intensive shooting, you get the ability to read the conditions during the mirage times, and feel your ready go to the next step.

That step would be to go back to the range and get some experience just after the sun disappears. You'll want to unmercifully kick the cat when you get back to the house.

Another trick is to set the side focus at distances between you and the target to see where there mirage is the heaviest.

My biggest problem with mirage is that it makes any scope look like junk when the target is vibrating as though its connected to the case tumbler.

Sorry for no real specifics as the above is all of my experience. Don't wear out a hunting gun learning how to treat mirage and wind.

What will really open your eyes is when you have an elk in the winter in the spotter with very seemingly stable atmos conditions and all of a sudden he looks as if he's been hit broad side with your big gun, that is ripple from one end to the other. That would be a dustless dust devil going through the canyon. That really sux.
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Old 07-21-2010, 01:08 PM
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Re: Mirage help...

Thanks, Roy. Good read. I just hope that what I was seeing was from mirage as I was a bit concerned about 3/4 MOA 2 -shot groups... Would need to shoot it at much longer distances to know the story if it wasn't mirage causing the issue the other day.
__________________
In the beginning God created the heavens and the earth. Genesis 1:1

"And can the liberties of a nation be thought secure when we have removed their only firm basis, a conviction in the minds of the people that these liberties are the gift of God?" Thomas Jefferson - Notes on the State of Virginia

www.wildsidesystems.com - Shelter for Your WildSide - http://www.youtube.com/watch?v=tYwgo...&feature=g-upl
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  #4  
Old 07-21-2010, 03:39 PM
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Re: Mirage help...

Trying to shoot here in Arizona in this heat is a Bitch. I go early in the morning which is still in the high 80's and shoot till I see mirage ( shooting at 300 yds ) then pack it in go home. It makes that orange dot dance all over the place and useless to try and shoot groups.
Tarey
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  #5  
Old 07-21-2010, 10:04 PM
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Re: Mirage help...

Roy, thanks for posting your thoughts and experiences with mirage...it can be a booger and I found what you wrote interesting.
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