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Drastic Impact Shift. Position vs Parallax vs Lighting?

rybe390

Private
Full Member
Minuteman
Dec 13, 2017
302
331
Hey all, I'd like to discuss something I have noticed recently regarding a somewhat drastic impact shift in my loads at distance.

To start, my data has been validated and trued. I've shot both my 140bthp and 140 eld loads in many conditions, and haven't seen much like this. I'm shooting at Pawnee Sportsmens Center in Colorado.

The past 2 range trips have been relatively cold, one of them being 15 degrees, the other 35. Baro pressure around 25.15. I noticed that when prone, I was seeing anywhere from 0.3 to 0.5 mil low impacts from what I should see at 500+ and beyond. I figured it was the temperature making my MV low, and figured out the MV difference would need to be around 75fps slower than my normal to see what I was seeing. It felt excessive. So, I busted out the Magnetospeed, and my MV was right where it should be. This rules out MV change due to lower temperatures. I then confirmed atmospherics, and I was on. I then, for fun, moved to the BC, it was a ridiculous amount to true so I threw that out.

I then decided, screw it, and stopped shooting prone. I moved from the right side of the range, to the left side of the range, and went from prone to a bench. My next set of shots was 4/5 impacts on 12" or smaller at 900 yards, with my original, confirmed data. From then on, all data was true, and I was making hits with my original data.

To me, this seems like 2 things could be going on. Either I was WAY off on parallax and my form was bad when prone, causing an impact shift. Or, there may have been some sort of lighting condition being that low to the ground, with the targets just above sight horizon, that caused a shift.

These are the only things I could think of that would cause a shift in impact like this, knowing that my MV was correct, atmospherics were correct, and data was previously trued. The thing that is messing me up is that this happened twice.

Has anyone experienced something like this before? Thanks for jumping into this rabbit hole with me! Just trying to figure out what may have happened.
 
Where I shoot most we quite often see about .8mil variation from confirmed dope. Especially when snow is on the ground. I also know it wasn't me or position etc because both of us were in the same place.
 
Snow can do some interesting things to light
Cold mirage as well.
When normal dope Is giving wonky results I always note light conditions and go down range to see what actually is happening at the target and on the path there if possible.
 
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