Let's Talk About Environmental Factors!

IdaRam

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So, y'all might be thinking I want to talk about the environment :sneaky: Nope, I'm talking about environmental factors that affect our ability to accurately put rounds on target! :D Sorry to disappoint you, but if we work at it we may still be able to start an argument ;) Just jokin' folks, not my intent.
Recently in another thread PHSC_Jono posted a great question about outside air temperature and felt recoil. DOC-404 posted up an informative article on environmental factors that effect accuracy and cartridge performance. Because of that thread I thought it might be an interesting topic of conversation.
Below is a list of some of the factors (environmental and otherwise) that affect accuracy, exterior ballistics and our ABILITY to shoot accurately. Notice I distinguished between accuracy and our ability to shoot accurately ;) Most of these factors don't really come into play until you start shooting at distances greater than what most people probably shoot at game. So this is really more about "shooting" than "hunting", but with the ever increasing popularity/hype surrounding long range hunting more and more people are shooting at game at greater distances. Don't mistake me for an advocate of this. At the risk of starting the first argument :whistle: in my opinion most of these folks have no business shooting at game beyond 200 yards. For those who actually practice extensively at longer range and have developed real skills, I have no issue with you.

Air density - Combination of temperature, barometric pressure and humidity (altitude and weather are the main factors that affect barometric pressure).
Distance - Range to target
Wind - Velocity and direction the air mass is moving which our projectile must travel within/through to reach the target.
Light - This one is a loaded subject!!! Where to start? Direct sunlight, cloud cover, intermittent sun and clouds, angle the light is coming from - high above, left, right. Difficult to quantify and little understood.
Mirage - Optical phenomena in which light rays are refracted and cause objects to appear distorted and displaced. Temperature, light, humidity, wind all come into play with this one.

OK, now here's a few I know are likely to start a fight :D Conspicuously left blank...
Spin Drift -
Coriolis Effect -


So I will start off by throwing this out there; I've always been intrigued with how "light" affects our shooting. I started shooting handgun metallic silhouettes when I was about 10 years old. After a little while in the sport I had been "adopted" by a few accomplished shooters that taught me a lot about shooting. One old NRA High Power shooter gave me some coaching on shooting on the days when the sky was full of big puffy cumulus clouds and the sun was continually ducking in and out behind the clouds. Enter in the old High Power shooters mantra "One up - Sun up". Meaning, compensate 1 MOA when the sun is beating down from above 'cuz you're going to shoot low if you are zeroed for different conditions. This is NOT confined to open sights, it affects your shooting with a scope as well.
I've had the pleasure of volunteering my time as a RO (Range Officer) at a number of matches over the years and to score a bunch of targets. One of the things that has been very interesting and educational has been watching the results from what is a very common 1st stage of the day at many Sniper/LRTR matches, the "Cold Bore" :sneaky: This is generally 1 round, first round of the day, either a "hit" or a "miss" - score or no-score.
Some things have become predictable. Many shooters do not consider the "light" condition. If it is early am and you are shooting north or south, the light will be coming in from a shallow angle from the side if it is a sunny day. Here in the northern hemisphere if you are shooting to the north the sun will be coming in from the hard right. Guess where 80% of the shots go... Usually about 1 MOA to the left.
Next time you are out at the range shooting some paper on one of those intermittent sunlight days, take the time to do a little experimenting. Shoot a 3 shot group while the sun is behind a cloud. Wait until the sun comes out completely then shoot another 3 shot group in the direct sunlight. See if you don't get a point of impact shift.
And when you are working up a load and shooting for group, keep the changing light in mind.
Past my bed time, but I would love to hear other peoples opinions, experiences, questions, etc about this and any other factors that affect our shooting.
Cheers!
 

enysse

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Never thought of light affecting a shot at all. To my knowledge it has not affected me. Wind is a HUGE problem, I try to shoot with or against a wind current and avoid side wind drift. It's not so bad with big guns but the small calibers you will be off by feet ( unethical in my humble opinion).
 

JTEX

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IMO light is only a major consideration with open sights. Wind? Within a couple or three hundred yards it would take a hurricane force wind to have a bad effect on big game shooting, match shooting is a whole different critter. Reasonable distance is actually the easiest IF wind isn't a factor, physics work!

Corriolis effect? Over 1500yards?
 

PHOENIX PHIL

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I don't doubt any of the things on your list @IdaRam have an effect. Spin drift and coriolis effect are real, ask a trained sniper. But those are very long range effects.

Air density from what I've seen will affect the bullet's travel even at reasonable hunting ranges however. Sight in at a low elevation and then move up several thousand feet and you'll see differences.
 

IdaRam

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Agree with you JTEX, distance/trajectory is not the biggest factor. It's the wind that gets ya when the distance gets stretched out.
Generally speaking, most shots at game are taken at pretty close range. Less than three hundred yards for sure and I bet if the truth is known better than 80% of shots on game are inside 200. So, it's pretty uncommon for any of these factors to come into play in most hunting situations.
Here's something to consider however. A lot of us are handloaders. When it comes to load development and testing we put a bunch of time, money and effort into tuning our guns and loads to near optimum performance. Understanding the potential effects of all the factors that come into play will make us better handloaders as well as better shooters.
I wonder how many shooters chalk up an errant shot to just being a "flyer" for unknown reasons when it could have been something explainable if we only understood more thoroughly the factors in play?
I purposefully chose to post a couple thoughts on the effects of light because it seems to be one of the least recognized as being a factor. I'm no authority on the subject but I have done quite a bit of experimenting with both open sight guns AND scope sighted guns regarding the effects of light and point of impact shift. I'm not convinced that all the same factors apply to both open sights and scopes, in fact I don't think they do, but I am convinced there is an effect on both. I've been able to replicate and eventually predict the effects too many times to be convinced otherwise.
Some folks say hogwash! And others are firm believers. Regardless, it's always interesting to hear peoples opinions either way.
And yes, JTEX, I did notice you said major effect. :D Rogerthat. It's not a major effect, unless you're 4 rounds into a .100 group and the sun pops out from behind a cloud.
Take this for what it's worth; I shot a sniper match years ago and competed against a team that had won a world championship in Austria. Both members of that team were firm believers that light has an effect and is a factor to consider. Sorry for the chest thumping here, but my team mate and I finished in 2nd place behind this team.
Coriolis effect? Spin drift? (n) :eek: I know, I know! :D I have the same reaction. Jeezus! Just how far are you shooting? :eek: But do you know how many times I have heard people refer to these 2 as being factors? How could I not at least throw them out there? And there are ballistic programs out there that allow you to compensate for them so they must be a big deal, right? :sneaky: OK, for the CheyTac shooters, maybe...
Agree with you too PHOENIX PHIL, some of the things that effect zero like altitude and humidity can make you a believer in Mr. Murphy (y)
Thanks guys (y)
 

JTEX

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All well stated Ida. I certainly agree with you statement on handloading!

At my club we can and do shoot out to 600yds and I travel a couple of times a year to a place I can shoot out to 1000yds or better. I shoot RUMS, Edges and Lapuas and the common stuff. I play at the BR game a bit and am very familiar with what wind can do ( ain't that great at dealing with it, but am aware and at times aghast! ), even at 100 yds. I shoot several 6BR, 30BR and 6PPC in a Stolle Benchrest setup, watching and trying to interpret 5 windflags on a 100 yard range can drive you bugsh*t.

I'll bet you a quarter that 90% of people claiming "Coriolis and spin drift" are REALLY complaining about a canted scope or rifle, now we're not talking about competition shooters here, this is a hunting forum. When I hear the coriolis thing I will usually ask what compass heading they were shooting, and they usually ask me why that would matter............. I try to keep my longer shots headed East or West:whistle:

I know we can and do learn from the competition shooters and shooting. I also think at times we can over think it at far as hunting accuracy goes though.......

The "light" thing with a scoped rifle will take some studying on.

Mirage wasn't mentioned much above but I see, constantly, mirage affecting shot placement quite a bit, just haven't noticed "light" making a difference yet......

All good stuff and I like to hear opinions, thanks!
 

CAustin

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Ida it all impacts me that's why I must practice!
 

gillettehunter

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In Wyoming wind is a problem...... A few yrs ago I killed a antelope in its bed at 230-250 yrds. Can't remember the exact number. We lasered it at the time. .270 WSM w. a 140 gr bullet around 3000 fps. The wind was over 20 MPH approaching 30. I had about 16 inches of wind drift....
Like mentioned elevation makes a huge difference. I'm hunting around 4500 ft close to home. In the Bighorns I often hunt close to 10,000 ft. The difference is amazing. Bruce
 

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