Mirage

[haroldclark]

This post was made on the Cast Bullet Discussion.  I thought it might be of interest to the TC Shooters too.  The original post is pasted below and my response below that.

Posted: Mon Nov 29, 2004 6:22 am    Post subject: Mirage        

--------------------------------------------------------------------------------
 
I'm working my way through "The Bullet's Flight From Powder To Target", and it ain't easy. Franklin Mann discusses mirage on pages 177-180; describes his testing, and concludes that "...no mirage could be detected, in slightest degree, to affect telescope lenses or change the position of cross hairs on target up to 200 yards."
I've read the section many times, and think that I understand what he said and what he did.
His conclusions seem to fly in the face of the conventional wisdom concerning mirage. Could all the more recent work that I've read about shooting in mirage be wrong?
joe b.


Harold Wrote:
Mirage.

If I understand the statement in your question, the person asserts that "...no mirage could be detected, in slightest degree, to affect telescope lenses or change the position of cross hairs on target up to 200 yards."  

I have played with the study of Mirage for the past 3 years and 2 days a week.  The Mirage is an interesting phenomenon.  Mr. Mann is somewhat right about the 200-meter distance of 200 yards.  However, it would depend upon what you are shooting.  Mirage raises hell on a 22 Long Rifle at 200 yards.

What is mirage?  Mirage is a series of wavy lines in the “Air”.  The lines may move right, left, upwards or in any degree of angle from the earth surface.  When the Sun is shining on the earth, the surface is heated.  The heated earth creates wavy lines going straight up as the heated air rises from the surface.

If there is a slight wind, the mirage will go from straight up to the direction the wind is blowing.  It may appear to be horizontal in a heavy wind or at any angle covering the 180-degree flat surface of the ground.  It can reverse direction in a moment without considerable notice.

A fast moving bullet will still be subject to the disturbance that we see in the Mirage.  Actually, the reason that the Mirage is moving other than straight up is the wind.  The wind will affect the path of a bullet to a degree, depending upon bullet weight and velocity.  The mirage does not actually affect the Point of Impact.  The cause, that makes the mirage move, does in fact cause a different POI of the bullet.

When you are reading the Mirage for left to right movement, you are in fact determining the severity of the wind affect on the bullet travel.

Mirage and elevation:  This is a tricky subject and a lot of people may not agree with me.  As I have declared, I have spent several years spotting for numerous caliber TC Contenders, Encores and rifles up to 45-100 BPCR.  I have made a study of the effects of Mirage.

Example:  Let’s say that the mirage appears to be rising at a 45-degree angle to the right at 500-Meters.  The mirage is best read with some kind of a background, like the Target Rail, that is black or a dark color.  The mirage reading says that the wind is blowing the vertically rising heat waves sideways and makes them appear at a 45-degree angle to the right.

Now, lets really talk about what a mirage is.  A mirage is an image created in this case by the heat waves and the wind blowing it.

When I first started noticing what the mirage was telling me, we had been shooting all morning at 500 meter Rams and punching them dead center with 308s and 7mm Mausers.  The temperature was cool and comfortable.  We took a lunch break and exchanged lies for about an hour.  We resumed shooting and the perfect shooting rifles are now hitting 2 feet high and a foot to the right of the Ram’s head.  Out of absolute frustration, I held the POA at the foot of the rear leg.  The ram was facing right on the railroad rail stand.  I hit the Ram high and slightly right of dead center.  My buddy did the same thing and had hits too.  

What happened?  The sights had not changed during lunch, but the heat of the day changed and the wind from the left came up.

My theory on this situation is that the Ram didn’t duck or move, but the picture (Mirage of the Ram) moved with the rising heat waves that are being blown right at a 45-degree angle.  If you aim at the Mirage, you will, in-fact shoot where we see the Mirage Picture.  When the wind blows strong enough from the left, the mirage lines will spread severely and appear to be moving sideways.  In this circumstance, you are fighting the Mirage and the Wind.  I have held as much 8-feet left with a slow moving 30-caliber bullet (2000fps).  Did a 10 mph wind move the bullet 8 feet or some portion there of?  Or is it a combination of the Picture Mirage moving and the wind also affecting the bullet drift?  I personally, think it is both.  If I know my firearm or another person’s arm, I can look at the mirage at 500 meters and call your POA for a hit, depending on the reading.

Two days during the week and 2 additional Saturdays a month, you will find me at our shooting club.  I shoot and my buddies continue to hone their skills at reading the mirage and wind.  They shoot and I spot for them.

We have done the 1,000-yard Black Powder Cartridge three-day match and I spotted for two shooters.  Using my stated theories above, they came in 2nd and 3rd place in the State Championships.

I do not proclaim to be an expert in this field, but I have paid attention and have made a sport of spotting and calling shots for myself and other shooters.  It is an art form, much to my dismay.  I would prefer that it was logical so I could analyze and make a calculation from my findings.  Well, that is not happening.

I hope this has been of some help to you.

Harold Clark

[Duffy]

Harold,
Do you think that optics magnify the mirage affect or just make it more noticeable? As an example if you had to aim 2 feet to the left with a 12X scope would it be the same with a peep sight or would it just look different and you would still aim at the same point as with the scope?

[haroldclark]

Duffy,

The affect of the mirage is always there.  You normally cannot see it with the naked eye.  With peep sights, like on 45-70 Black Powder Cartridge rifle, I cannot determine mirage.  The magnification of the scope or spotting scope allows you to see the mirage (I'm referring to the waves made by the heat and wind).  The power of the scope doesn't change the mirage view.

Example:  My buddy, Gerry, is shooting with vernier scaled peep sights on his BPCR.  He can read the wind flags, but he can't tell what the mirage is really doing.

I watch the conditions including wind direction, wind strength and the mirage.  Before each shot, if needed, I tell him what sight changes are needed to hit the target.  I may say " Give me 2 minutes of left and one minute down" as an example.  Sometimes the mirage will change directions before he can get the shot off and I call a "Hold that Shot" to prevent a miss.  We either wait out the change or make a sight change to compensate for the mirage change.

The only time that too much magnification becomes a spotting problem is in the high heat of the summer and the heat waves are rising from everywhere and too much power becomes opaque (bathroom window glass).  Where I live, 105 to 110 degrees is common in the summer.

No, changing your power on your scope from 5 or 6 to 10 or 12 power will not change what you see in the mirage.

I hope I answered your question.

Harold Clark

[Duffy]

Yep!  The problem exsists even when you can't see it. I just didn't know if the poa would be the same for the two. Eg. scoped rifle needs 2 min left and so would open sight under the same condition.
I know what you mean about the opaque effect, it happerns here quite a bit during warmer months too. The flat wheat/summerfallow fields really put off a bunch of waves as the day progresses and in the summer your done shooting by 9 or 10 am. Of course I'm usually havesting and don't get to shoot then anyway.  

[mamerch]

Mirage is simply the distortion of your view of an object.  Distortion of your view does not affect the flight of the bullet.  The flight is exactly the same whether there is a mirage or not (varying slightly with the wind).  It seems to me that I never see a mirage image in the distance when there is a strong wind.  I only see them with a very slight wind or no wind at all.  
My bet is that if you use a machine rest and a single stationary target you could shoot one shot every 30 minutes all day and never get a huge variation in point of impact except for the few inches that are induced by wind or fouling.  Mirage can be a problem if you shoot long distance on hot days.  The mirage doesn't change your point of impact but it does make you move your point of aim to someplace where your intended point of impact really isn't.  The other mirage problem comes from strings of shots heating up the barrel to the point that the heat rising from the barrel creates it's own mirage effect with your sight picture.  this effect still doesn't change the poi, just the point of aim by making your target appear to be somewhere it isn't.  

Just my thoughts, not real complicated.  Maybe some folks can "read" mirage's just like doping the wind.  I can't.  Could probably learn to if I had time and money to shoot enough.  Uncle Sam, my wife and four kids ensure that this won't happen for at least 40 or 5 more years...

mamerch

[mamerch]

that last sentence should read "4 or 5", not "40 or 5" although sometimes 4 can seem like 40 when you work for Uncle Sam or are married or BOTH!

mamerch

[haroldclark]

Mamerch, you have describe what a Mirage is very well and so simply, I would like to use your description in my explanations, if you don't mind.  In order to read a mirage and the wind interaction you must use a spotting or rifle scope unattached to a heated barrel.  Also, there must be a dark or darker area than the general terrain to view the mirage.  For example, if there is a tree trunk or a grove of trees you could use that to read with.  However, where I have done my testing, there is a steel railroad rail suspended at least one foot above the ground and the backstop Burm with dark colored dirt.  The two provide an excellent viewing area.

The originator of this conversation on the Cast Bullet Discussion wrote and I responded below as well:

Posted: Wed Dec 01, 2004 1:31 pm    Post subject:          

--------------------------------------------------------------------------------
 
I have messed around with crosswind tests using my 45 colt and that's interesting. Behind my shop I have a clear shot 1/2 mile field and on a windy day (15-20 mph) I lobbed some out to around 500+ yards. Using the impliment tracks as somewhat guides some of those slow moving bullets were moving over as much as 50 feet or better.  It was a learning experience and quite fun to try and outguess the breeze.

Ryan
 
++++++++++++++++++++++++++
 
 
haroldclark
Location: Northern California
Gender: Male Posted: Wed Dec 01, 2004 2:19 pm    Post subject: Riding the Heat Waves        

--------------------------------------------------------------------------------
 
That thought brings to mind another adventure with wind and etc. One day I was shooting my favorite 30-06-cast bullet rifle at 420-yard turkeys. That day, we were experiencing a headwind of about 7 to 10 mph. When the wind is from left or right, the rifle will hit all targets out to 550 yards with a 173-grain cast bullet with the correct windage call.

However, between the firing line and the Turkey line is a 20-foot Burm backstop for the 200-meter chicken line. On the backside of the burm it is angled up about 45 degrees. When the wind blows from behind the burm, the wind is compressed until it launches upward. When my bullet crossed the burm, the upward motion of the wind would give 19 or more inches of lift to the projectile. If the wind ceased, I could hit the Turkey.

To further confirm this action we aimed at an object that was away from the burm, yet out to 375 yards. At that target, I shot a 5" group with the headwind. I shot at the 420-yard Turkey and shot 19 inches high on average. I then turned to the 330-yard pig line with no burm in front of it and knocked down pigs without difficulty or sight changes to compensate for the wind. Of course, I set my sights for the pig distance before shooting.

When there is a tail wind or wind from behind us, we experience the same, but different, lift from the front side of the burms. That story has yet to be verified in inches fo bullet travel. It still makes me crazy trying to figure out what to do.

Keep reading the wind and mirage.

Harold Clark