Why elevation changes between shots at 1000?

[Creedmoor shooter]

So I went out today for some 1000 yard practice. Had wind gusts up to 15-20 mph and it was 30°f. The wind was only a slight left to right angle but mostly to my back so I held a 1-1.5 moa left hold for wind. I had my windage nailed first shot just 1moa a under my milk jug. Did the same hold to confirm and the bullets were 2in apart. So I held one moa high and then my bullet goes 1 moa over the target. Confused I went back to my original hold and it went low again. At any rate my next 7 shots bounced back and forth between 27.75 moa to 29ish moa. Im slightly confused as my windage stayed good. Does anyone know what may have caused this? I'm wondering if it could be inconsistent pressure on my rifle as I was wearing a thick coat.

 

[Canhunter35]

Was there a hill of some sort behind your target?
If so, it could be causing vertical swirls that rise and fall in tempo, causing the elevation shift. Doesn't take much of a hill either to cause that in 20mph winds, especially if they're behind your back
That would be my guess from what you're describing

 

[Timber338]

Was there any correlation between barrel temperature and high vs low impact? Possibly heat stress on the barrel causing a change in velocity?

 

[Creedmoor shooter]

Was there a hill of some sort behind your target?
If so, it could be causing vertical swirls that rise and fall in tempo, causing the elevation shift. Doesn't take much of a hill either to cause that in 20mph winds, especially if they're behind your back
That would be my guess from what you're describing

Actually yes your correct. I was shooting over one hill then my target was placed on the next hill over. That would make sense

 

[Creedmoor shooter]

Was there any correlation between barrel temperature and high vs low impact? Possibly heat stress on the barrel causing a change in velocity?

If this was the case my impacts would keep going higher but they didn't. Sometimes they'd land low and sometimes high. I shot all 10 rounds in succession

 

[Canhunter35]

Actually yes your correct. I was shooting over one hill then my target was placed on the next hill over. That would make sense

I've experienced that several times...**** wind.
It's really bad with a 308 and 168pills lol

 

[Creedmoor shooter]

I've experienced that many times...**** wind

Let's just say it kicked my butt today! First time I've ever failed the milk jug challenge

 

[Canhunter35]

It's hard to dope correctly when it's that strong. I just sent my rifle away to get a new 7mm rem mag barrel to shoot the 180eldm, I'm upping the anti against the wind lol

 

[nmbarta]

How good is your SD/ES with that load?
When I see vertical spreads at 1000 is it almost always my load causing it.
Could be brass that's getting close to it's end causing inconsistent neck tension, (I don't anneal)
Could be a dirty barrel causing velocity spreads.
Could be a new lot of powder/bullets/brass.
a 30fps spread with my 7mm will cause around a 7" vertical spread at 1000, combine that with tail wind going over a hill and you've got your 12" of vertical easy.
This is why I'll usually take the load with the lowest sd's even if I have a load that shoots slightly better at 200.
I'd shoot a few over the chronograph just to rule that out, if your sd's are good, it's probably just wind, weird things happen at 1000+

 

[Creedmoor shooter]

How good is your SD/ES with that load?
When I see vertical spreads at 1000 is it almost always my load causing it.
Could be brass that's getting close to it's end causing inconsistent neck tension, (I don't anneal)
Could be a dirty barrel causing velocity spreads.
Could be a new lot of powder/bullets/brass.
a 30fps spread with my 7mm will cause around a 7" vertical spread at 1000, combine that with tail wind going over a hill and you've got your 12" of vertical easy.
This is why I'll usually take the load with the lowest sd's even if I have a load that shoots slightly better at 200.
I'd shoot a few over the chronograph just to rule that out, if your sd's are good, it's probably just wind, weird things happen at 1000+

I honestly don't remember my es or sd. I'll have to dig up my old notes. I have shot this load a few times at 1000 and it's been very good with very little vertical difference. I'm still using the same lot of powder and bullets as I have previous. Barrel was cleaned not that long ago. Brass is once fired and annealed. .003 neck tension.

 

[Creedmoor shooter]

It's hard to dope correctly when it's that strong. I just sent my rifle away to get a new 7mm rem mag barrel to shoot the 180eldm, I'm upping the anti against the wind lol

That's the next build on my list. That's a wind bucket right there. I'd be doing a 28 nosler if the brass wasnt so dang expensive

 

[lancetkenyon]

Wind does weird things that you might not anticipate. Fluctuating winds cause more than just left/right impacts.

 

[Creedmoor shooter]

Wind does weird things that you might not anticipate. Fluctuating winds cause more than just left/right impacts.

Looking at that it was about a 7-1