Long range target shooters, is it light, is it temperature, is it mirage, .......

M

Michael J. McCasland

New member
The question of the day for you long range shooters. This is not a rifle problem, nor is it a scope problem, nor is it a ammunition problem, it is an interesting problem none the less. The setup - I'm at the range shooting a fun little competition. This is very similar to the balloon shoot that the Varmint Hunters Association puts on every year. It consists of shooting 4 or 5 inch balloons from the bench at 200 meters (4 balloons - 5 points apiece), 300 meters (4 balloons - 10 points apiece), 389 meters (5 balloons - 15 points apiece) and 500 meters (5 balloons - 20 points apiece) The 500 meters target is an actual distance of about 540 yards. An accurate rifle is a must for the 500 meter balloons. And I have a rifle that is up to the task.

Now for the problem - At 7:30am my predetermined scope settings are dead spot on. By 9:00 when my turn at the range comes up my bullet impact is high enough to create problems on balloons and is completely out of the balloons from there on out and I need to absolutely guess at scope settings from there on. At 11:00 things are completely out of hand and everythings shooting very high. The rifle is dead cool, the ammunition has been kept out of the sun in consistent coolness (under a coolldamp cloth). So it is not an equipement problem. Once new settings are figured out the rifle is still a balloon killer.

The Question - Many theories float around at the range as to exactly what is going on (everybody is having the same problem and this happens EVERY time we shoot the match). I do not know what to believe. Wind is moderate and manageable, the light is bright, mirage is out there but not horrible. Is this a factor of the relative brightness of the available light, is this mirage, is this simply a factor of heavy morning air vs hot light air? Is there a constant that will make reasonable educated scope setting guesses possible?
 
Welcome to the real world, the sun's relationship to the sights is very perplexing. Brightness, intensity, angle in relationship to muzzle makes a lot of difference in bullit impact. It is not mirage, and only shooting at different times of the same day at the same target and keeping a log will help, I feel it is much harder than doping the wind. GOOD LUCK
 
Good one Michael, living in Arizona when is it not HOT? I think you answered your own question, well what you have said sound good for me.
heavy morning air vs hot light air
Click to expand...
I would have to agree with your quote as I pick. :rolleyes: Sorry not much help.. But it sounds good to me. Jack Robert's has more in this field then I. I am not a bench shooter, I have seen the big difference in temp as you have notice as well.
 
Mirage, wind, barometric pressure, and temperature will mess with your mind. /ubbthreads/images/graemlins/wink.gif

This is where the bench boys earn the big bucks.
I can't give you any kind of formula that would do you any good. Too many variables, including altitude.

There have been a few times I have wanted to wrap a 3000.00 rifle around a steel pole for shooting only a half inch group.... /ubbthreads/images/graemlins/laugh.gif

As was stated above, this is where you keep a log, or make a mental note. If you are shooting at the same place every year, keeping a log that includes the temperatures would help you big time.

Bench guys do not care if they are on target necessarily, they are looking to repeat everything they do with each shot exactly, including paying attention to pressure points, and where their rifle sits in the bags. This will give them the tightest groups. They are not really interested on where the bullets impact on the target as long as all shots stay in one ragged hole.

I would suggest going out to somewhere close to where this balloon shoot is held. Bring a laser rangefinder to verify the ranges and temperatures.
You will learn when to adjust your elevation knob. Heat can play a big factor even if you are keeping things in the shade.

Hope this helps some... -MP
 
When I used to shoot metalic silhouette, one of the first things I learned was that your bullet tends to follow the sun. In other words, if the sun is straight up above, you will hit high. Sun high left, bullet high left, etc. This of course assumes you sighted in with the sun at a different location than when you shoot for score. There were different theories as to why this happened. The most popular was gravitational pull from the sun. Don't know if that's the case or not. I would try to practice at as near the average match time as possible to help overcome this. I also recorded the number of clicks I adjusted my sights for each distance we shot at. We always got sighter shots before we shot for score. That way you could adjust your sights the same for each distance, no matter where you happened to start from.
That's how we did it. Hope it helps.

Paul
 
You didn't say the lay of the course, if it is East to West? The problem could be polarization of light through your optics as the sun gets higher in the sky. Any photographer will tell you the sky in the North is always more blue than the Southern sky...if you are North of the Equator. Red and blue wavelengths will change the focusing plane of a lens accordingly and that could effect aim point. Just a possibility. Hope you find the answer.

I have enough problems hitting a 300yd target, no less a 500yd target! Ha..Ha

Nikonut
 
Michael J. McCasland: You may very well know some of the points I will make.I have found when shooting at long distance under conditions with mirage a spotting scope will be needed to give you the details necessary to use mirage as a indicator for sight correction. With mirage the rising air of one temperature is mixing with air of another temperature and air density is in the process of change also. From you the shooter to your target and all the ground between. As you and others have posted this condition will refract light differently.Turn your spotting scope so you are not looking at the mirage stright on but at a angle look at the detail of the mirage and the detail at points down range to your target. This distortion from the rising air and and air pressure will cause your bullet to shoot high. The conditions you talk of in your post will in exteme cases cause a bullet to shoot high over the target. My advice use a spotting scope and learn about mirage and how to use it as one tool in your bag of tricks. Point #2. As humidity goes up air density goes down. You may have read or had someone tell you different. The truth and fact is, as humidity increases air density decreases bullets will shoot high. Drier air is very dense bullet impact will be lower. Point #3. Wind value. In my view you must have wind value adjustments for both horizontal deflection and vertical deflection. The values must be broken down for all oblique angles. Not just full value and half value. The more accurate your wind deflections are the more accurate you will shoot. As the range (yardage) increases so will the need for accurate adjustments.I use a wind clock for wind value deflection and my down range accuracy has improved. Look at the details in the conditions you are shooting in. In my part of the world I shoot in heat above 100 degrees by mid afteernoon at times. The conditions we all shoot in are minute to minute conditions. Some points that I hope will help you. I wish you the best Michael lane
 
pokerplayer - You are most certainly correct. Wind I can deal with. This type of possibly optical deflection is much more difficult to figure out that wind.

Here's an additional question - I use a 36x target scope. It brings things up close and personal but does a high power scope multiply this effect like is does mirage?
 
I'm waiting to hear what Jack has to say. One thing I thought I'd toss out to chew on while I'm waiting though.

Years ago, there was a PS article about this. In it, the author asked a panel of experienced long range competitors and some optical industry people for opinions. To make a long story short, there was a variety of opinions. One of the pet theories involved the changing light conditions causing an optical "shift" in the apparent target position, very much like what happens with mirage. The author came up with a way to test this theory. He solidly anchored a scope in his house with the crosshair fixed on a point a good distance away - I forget exactly how he anchored it, but it wasn't going to move. Then he checked it regularly, through a very wide variety of weather and light conditions to see what effect these conditions would have on the aim point of the scope. What he found, was that the aim point never moved, at all, basically shot the pet theory down in flames. Leaving him without an answer...

- DAA
 
Michael J.McCasland: If you do not mind the information what cartridge and load are you using for this shoot. Have you a performance baseline for this load and at what temperature, humidity conditions were your baseline performance established at. I would like to know more about your load to put in contex your problem.Any adjustments will be made off the performance baseline you start with. Thanks Michael Lane
 
DAA - Now that is interesting and it brings something to mind. While I was working for a land surveyor(gota be careful about how I describe my position on a survey crew you know /ubbthreads/images/graemlins/smile.gif ). Frequently we shot distances and more importantly angles at much longer distances. We had to deal with mirage and other such problems that shooters have to deal with. But for mirage we simply shot the average. The math prooved that this was more that acceptable and very repeatable in different weather and different light conditions.

I am considering that the differance must be attributable to the conditiond that the bullet encounters on its way to the target. Light/heavy air, air rising from heated/heating ground something or other else that we don't know about. I don't know but all of the answers so far are very interesting.

I can't help but to wonder how much thi sort of effect plays a part in the various posts that tell of shifting "0's", real or unreal scope problems and other posts like that.

These types of shooting competitions interest me because they actually closely imitate what you will encounter in the field. No time for sighting shots, just a simple situation of sitting down, finding a shooting position, taking your best guess and shooting away. Yes many of us have range finders and wonderful things they are. However I am finding that even with the very best predetermined range scope settings long range shooting is much more of an art than a science. Great fun isn't it?
 
Michael Lane - You were typing while I was typing.

The rifle is my much talked about 223 Ackley Improved. Right now I'm shooting a Hornady 68gr Match Bullet at close to 3200fps (chrony) 10' from the muzzle. This load is not my best 100 yard load but the bullet preforms at distance very well. I'm planning to do a day long test. Start at 7:00am and find my scope settings. Do the same at 8:00am, 9:00am, 10:00am, on and on at appropriate times until I have a good bench study to work with. Right now I have scope settings established at 7:30am (temps. in the 70's - mid. 80's) or so and in the for trips to matches they were amazingly accurate but in the hour or so it takes to get the match started and my turn comes around (temps in the mid 80's - mid 90's) things change.
 
Michael J. Thank you for the post and the added info. Your post is great and something I have questions about and have had problems with myself.If you have read my post you and I are on the same sheet of paper so to say as to cause and effect. I have done the very thing you are going to do. This will help you greatly. You will see and have a baseline to work with. Your adjustments will be made off this baseline and data you get at each shooting oppurtunity. I have a question for you. Your load chronographed will give a very good idea of pressure of your load vs factory loads of same bullet weight.The problem in part is to know how temp will effect the pressure of the load your using. What are your thoughts . Thanks Michael lane.
 
There is not much I can add that has not been said. My favorite theory was mirage until that was shot down. It is still hard to believe that mirage doesn't really move the bull after watching it bounce around in the scope like a ping pong ball dropped in a sink.

I did run the numbers for the load listed above and all else remaining constant, raising the temperature from 70 to 100 will raise the point of impact 1.1" at 550 yards. On average, the humidity does not increase with increasing temperature, so that normally would not be a big factor.

A crosswind will also cause vertical deflection. I do not have numbers at hand for the 68 bullet, but just as an example here is the 168 MatchKing;

The 168MK, fired at 3050fps, from a 10" right hand twist barrel, will deflect 30.3" at 600 yards in a 10mph wind. It also will deflect -2.6" if the wind is from left to right and +2.6 in a right to left wind.

So, rather than one explanation, it is looking more and more like a combination of several smaller things. To insure that first shot in the 10 ring, there are a lot of things to consider.

Jack
 
Let me be specific in expanding my questions for you or anyone else. One key to accuracy at long range is pressure of the load your using and how that load will be effected by temp humidity over all conditions your shooting in at the time. Agree or not the only way we as handloaders can get a idea of pressure of our handloads is over a chronography. Taking head and case expansion numbers from fireformed cases give us mixed results. chrono handloads vs factory loads is the best we can do with out lab conditions and saammi pressure loads agree or not. Based on this is it not best to get baseline for our long range shooting based on chrono numbers vs factory to get pressure, velocity. then work on just a 100 yard target in all shooting conditions, data factored in at longer range and adjustments made off that data . As temp changes should we not have a solid 100 yard baseline to work adjustments off of for longer range. The key as I see it the work done on data for our specific load at the 100 yard mark this is the baseline for all adjustments for longer range. What ever load specific powder primer bullet OAL we use at the 100 yard mark. The data over the scale of temp humidity changes air density wind deflection vertical deflection at the 100 yard mark will effect adjustments long range. My point is this if one gets all data for the 100 yard mark for a given load with knowen pressure temp humidity deflection angles as baseline then all adjustments after the 100 yard mark should be based on solid data. Should baseline for a specific load under all factors be based on the 100 yard mark and adjustments made off that data. I will be the first to say I am not the best at puting words and thoughts into a clear topic. I would like others to give opinion to this theory. thanks Michael Lane
 
Jack, I'm run ragged and trying to type this with my baby girl on my lap. So... Anyway, the article I was talking about did not discount mirage moving the bull at all. Far as I'm concerned, mirage does move the target and that is a fact. You might have been talking about something else though, like I said, I'm not all here right now...

- DAA
 
P.S. Michael, if you intend to shoot 500 yds, test 500 yds the 100 yd data might be useful but also might not mean diddly. Sorry to be short, just hard to type with one finger while keeping a 3 month old happy!

- DAA
 
DAA is absolutely right about testing at the distance you are going to be competing at. To do otherwise, will put you at an unovercomable disadvantage to those who test at, and practice at, the full distance.

Competition is serious and if you don't get real serious real quick, you do not really want to be a winner. You can win, but not without extreme effort. You should always realize that there are very many, very talented, very dedicated people, after the first place. To beat them, you will have to put out more effort.

Jack
 
I am with Jack and DAA on the mirage thing. I dont' care what they say, shooting groups in high mirage is next to impossible, even at 100 yards. You have no pin-point spot on the target to shoot when it seems to be moving like a jumpin-bean! Also, head and tail winds do some pretty strange things when you add distance.

DAA has another good point. You have to shoot your loads and rife at the distances of the match in practice and at the match. Just like sniping, you have to write down every shot,account where it goes, and all the weather effects,good or bad, every day. When preparing for a match such as this, I would have the match set-up exactly on my range as there but the targets would be circles drawn to exact ballon spec's with some sort of aiming point in the center. This way I will have exact point of impacts for all shots to log. I will shoot it everyday rain or shine and note every shot

Dead on at 7:00am will not be dead on at noon and will change during the day as it heats up and cools down. As to how much it effects your rifle and loads will have to be figured out by you. Points of impact change with heat and cold. General rule of thumb is less humidity higher it shoots and higher humidity bullet drops more at long range. Remember, nothing is exact or the same. Only close if you are lucky!

The last thing and foremost on my mind is, "Does your scope track properly everytime." I have tested every target model on the market for the last 20 years and there are very FEW that can or do! This would be the first thing I would check if you are an experience shooter. Do a simple 10" square test on it at 100 yards at least a couple of time and 200 too. If it can pass this, then welcome to the real world of long range shooting where the difference between the men and the boys is knowledge and luck!! Or at least that is what the old'timers always told me!! I am fortunate enough to know some of the best shooter in the world and they still have trouble too!! Good Luck!!! Sorry can't be of more help. This is one of those impossible questions we all want to know the answer too.
 
And that is exactly why the question was posted. Shooting at distance is not as simple as cranking in elevation clicks, holding steady and showing good follow through. When given a known acurate rifle lots of folks believe that these skills are all that are needed to compete or kill successfully at relatively long ranges. Now take that coyote standing out there at bragging distance. Say beyond 300 yards. Are you sure that you want to take that shot without the controlled field experience you gain from the relatively controled experience of shooting from the bench?

Now as to the controls that Michael L. refers to. Special attention was taken with the loaded cases, they were kept cool and even down right cold to the touch (not too cold) until the match so the cases/powder/bullets were of very constant temperatures through the entire shoot. Scratch the varying pressure due to changing heat as it relates to powder theory. The rifle was not kept cool but it was kept out of the sun and felt cool to the touch (Saturday was not a hot day, at least relative to what we can easily find in Arizona) before each string. Thats why this thread started with several rifle/equipement disclaimers. The scope repeatability question is troublesome. The scope is a B&L Elite 4200 36x Target scope. I have not had this scope long enough to claim vast experience with it, but from what I can tell to this date it has shown remarkable repeatability. When establishing the origional scope settings and at each pre-shoot sight in it was run through all settings repeatedly, in both a random and progressive manner. The settings were even tested to see if direction of adjustment would effect the quality of the final settings. At this point I can tell no differance. Time will tell on this issue.

As far as establishing a "0" aat fairly short distance and having them hold true from there on out. Well this did not work. After finding a solid "0" at 200 meters the predetermined number of adjustment clicks were fed into the scope. Unusable results occured and a return to pre-determined settings had to be used to re-establish a workable "0". Actual field time shooting at distance will be a must for establishing scope settings at distance.

Interesting to note though. If I were shooting at a coyote standing out at the 540yd mark he would have been holed on each and every shot. The bullets were out of a very small balloon but would have made for a very bad day for a standing coyote.
 


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