Shooting through mirage (boil)

[Jumpalot]

So, I've run into this twice now. I was out shooting yesterday, upper 70's*, prone at 700yds. Little to no wind but what there was was coming from pretty much behind. Bad mirage, and hitting at least an MOA low. I had the same issue a few years ago. I've done some research, but everything I find, says I should be hitting high not low. I'm trying to shoot in different conditions to practice. Any help/experience would be great! TIA

 

[Broz]

I get the same results on steel as you do. 500 yards out impacts are a minute low in stiff mirage. I always just made it simple by thinking if it looks like the aim point is floating I will likely hit under it. On these days a target up off the ground, or a rock bluff are much easier to manage

 

[MontanaMarine]

When mirage turns the target into a dancing blob of color, it's hard to see, hard to hit, and hard to get visual feedback.

When your line-of-sight is close to the ground, it gets much worse. If you can elevate your firing point, the target, or both, it helps.

Here's a short clip where I was trying to make a hit at 1800 yards. Shooting the 215 Berger from a 308Win. Mirage was working against me, but I was able to get my LOS above the ground by putting my target (a small rockpile) on a hill, and putting myself also on a hill.

This is the target rockpile, rifle in the pic is a 223, not the 308 I used to shoot from 1800.

 

[Sled]

When mirage turns the target into a dancing blob of color, it's hard to see, hard to hit, and hard to get visual feedback.

When your line-of-sight is close to the ground, it gets much worse. If you can elevate your firing point, the target, or both, it helps.

Here's a short clip where I was trying to make a hit at 1800 yards. Shooting the 215 Berger from a 308Win. Mirage was working against me, but I was able to get my LOS above the ground by putting my target (a small rockpile) on a hill, and putting myself also on a hill.

This is the target rockpile, rifle in the pic is a 223, not the 308 I used to shoot from 1800.

nothing like a good fire to clean up a wide shooting lane for long distance work. nice shooting

 

[OXN939]

So, I've run into this twice now. I was out shooting yesterday, upper 70's*, prone at 700yds. Little to no wind but what there was was coming from pretty much behind. Bad mirage, and hitting at least an MOA low. I had the same issue a few years ago. I've done some research, but everything I find, says I should be hitting high not low. I'm trying to shoot in different conditions to practice. Any help/experience would be great! TIA

You're experiencing this because of the change in air density associated with warming. Warmer air is less dense, so things fall more easily through it- this is the same reason aircraft get relatively poor performance in hot weather. Warm air is also much more unpredictable, as different terrain features heat at different rates, causing thermals to vary along with their respective wind speeds.

 

[LaHunter]

You're experiencing this because of the change in air density associated with warming. Warmer air is less dense, so things fall more easily through it- this is the same reason aircraft get relatively poor performance in hot weather. Warm air is also much more unpredictable, as different terrain features heat at different rates, causing thermals to vary along with their respective wind speeds.

Warm air is less dense, that is correct, but this is not the reason his POI is low. Less dense air gives less resistance to the flight of the bullet, therefore it covers more distance is a given time. If you compare the flight of a given bullet fired from a given gun at sea level vs 10,000' ASL, the round fired at elevation has a flatter trajectory in this less dense air. Air is not dense enough to have a measurable effect on the 'rate of fall' of a bullet. Gravity controls that.

 

[OXN939]

Gravity controls that.

As it was taught to me, it's easier to influence the trajectory of a projectile when the medium it's traveling through is less dense. Any physics types wanna chime in?

 

[Jumpalot]

Great feedback so far! I guess my question is really around the research I have done almost unequivocally says I should hit high, yet I seem to hit low. Does shooting at 5000'+ elevation have anything to do with it? All I know is shooting through any mirage is tough as hell!!

 

[LaHunter]

Everything I have read says impacts tend to be high in mirage too. I agree, mirage is tough to shoot in especially when the target is dancing and changing shape really bad.