Range Report Dope OK, then not....

[jaybic]

Hello, I guess I am looking for some advice and I am not certain that I posted this on the correct page...sorry if that is the case but here goes.

I am shooting a 6x47L with 105 vld hunting bullets that chrono at 3070. This past Friday evening, I went and verified dope at a buddies place at 400, 600 ad 1200( I hit .1 low with 9.4 mils so I adjusted BC so that my Kestrel called for 9.5 and hit the waterline with a nice 3 shot group. Wind at FV 5mph R to L and all was where it should be. Next morning I head out to the match 3 hours away, shoot the first stage starting at 1158. Kestrel calls for 8.8 mils(seemed to me that I should not be .6 down for 1158 instead of 1200 but I dialed it and shot....way low...and the rifle shot low for the next 3 stages from 1158 walking in to 858. Kestrel aside, how does a rifle that is hitting on the water line 15 hours earlier end up that low?

a few details that my matter. the match was very sunny(mirage was present) and the sun was rising directly behind me and dead on to the target, shining on the ass of the bullet all the way in. The wind was about 5-7 mph and twitchy from and angle behind also. 80ish degrees...9am or so. My buddys rifle was also .3 low. the next day he shot a match and his dope was right back on? I have no idea what happened....what changed?

I even shot a KYL rack at 458 and couldnt hardly hit with a rifle that was completely doped the night before. Next thing I know, we move in to the 325 target on another area of the range and now I am running high and missing....

does keeping your Kestrel in your pocket heat it up and cause lousy dope? did sunlight play tricks on my eyes? Both?

This is not the first time I feel like i have had a rifle that had good dope and yet ended up with a pile of unexplained misses and then check the dope after the match and it lines up but if it is the case, how does a fella recognize what causes it and fix it before he tosses a match in the trash can?

Sorry for being long winded and thanks for your time because I am out of ideas....

Jamie

 

[Olen_4504]

as for your kestrel/pocket comment....yes.

you should LOCK your environmentals once you take them before putting the kestrel back in your pocket/pack/or lay it out in the sun.

then if it warms up or weather changes - put it back on live mode and re capture environmentals and lock again.

so this probably contributed to your problem. if that actually happened

 

[morganlamprecht]

the kestrel can be affected like mentioned

but also...sun into your face/behind you...ive seen it cause some weird issues

couple months ago, myself and buddy, sun setting behind us...shooting same load/velocity/etc...i had trued up at 500 yds and on a 10" plate at 800 yds the day before...next day, my buddy was needing .4 less for 800 yds, even tho we are the same velocity (velocity hadnt changed because we had a labradar running)...i said "no way"...i shot at 800...i was also .4 high...at 500 we were both .2 high...we then shot at 100, and both were dead on

we had a match that weekend and he was askin if we should adjust our dope...i said ignore it, cause math wise there was no way to get that to align....get the range day before the match, both of us are on from 400 to 1360

last club match we had was in the evening, final stages the sun was setting in front of the shooters, going down behind the berms...on the tower, the last squad, every shooter had to hold .2-3 low in order to hit the 400 yd TYL rack plates, when their dope had been fine for everything else 400 yds in the match

i like to verify zero/dope on multiple days for shifts like this...if you happen to zero/true in a shift condition, it can throw everything off...same if u zero in a good codition, and then get a shift condition during a match

ive been wanting to go out and shoot at a few targets facing one direction, at different times throughout the day, and look for any odd shifts, just havent had a chance to do it yet

 

[pitdog85]

I shoot in heavy mirage conditions all the time, for me it consistently pushes the bullet low. At 700 I have to come up anywhere from .2-.4 mil up from my clear conditions dope. Might be same for you?

 

[jaybic]

wow...just didnt see that coming I guess...I thought my gun went nuts, I forgot how to shoot...all sorts of things. gets in your head bad. How does a fella know when these situations are? how does one recognize it and adjust before pissing 4 or 5 stages away trying to figure out what went wrong?

 

[ShtrRdy]

Wow ( too )! Is there any information online that describes these sorts of affects?

 

[Olen_4504]

Buddy sent me this

 

[morganlamprecht]

yup, i remember when scott posted that vid...crazy things happen

i havent found anything that consistently needs correcting for, but i also havent consistently tried to find a relation in controlled conditions...i just noticed sometimes, things are off for every shooter, but others they arent....usually its sun low in front or behind...or shooting over close range ridge/hill, to a lower target

imagine...

X shooter here >>>
____ridge/rolling hill at 10-50 yds bullet barely clears the terrain____

**target @ 300+**

ive seen this screnario cause shooters to miss high also...even at 200 yds, one stage was a 200 yd, unlimited rounds, hit to move on...no berm and bullet splash hit 100s of yards behind the targets....shooters were dumping 8-10 rounds at a 3" plate at 200 yds and never touching it...one guy from the previous group came over and mentioned he had to hold .2 low to hit it...next shooter held .2 low and hit dead center...rest of the shooters followed, even the guys who had already miss a lot used their mulligans and hit it first shots

even the same range me and my buddy were both .4 @ 800 high during sun set...we've shot multiple times in the 30 min- 1 hr earlier time frame and havent had an issue since...the only thing that was different that one evening, was a cold front had come thru, but the sun was out all day...so it was warm during the day, and as the sun set, it went from like 75-80, down into the 50s...not something we can recreate for a while down here since its going to be 85-95 for the next few months im sure

 

[lte82]

Truing a bc at one distance is not really enough.

My method now involves getting a solid 100 yard zero, then shoot 300-500 to verify that elevation matches perfectly. I use a magnetospeed so my velocities are usually spot on, but I'll tweak it a tiny bit if my dope is slightly high or low at 500. Using out of the box BC's from berger, it's usually pretty spot on. Then I'll shoot 600 through 1000-1100 (every 100 yards if possible) and tweak BC to adjust elevation as needed to keep elevation POI centered up. Once I am happy at the max distance, I go back and run back through them all and make small tweaks if needed to clean it up.

A couple of things you can trip over:

1. Make sure you are truing your data with the firing direction set to the firing direction you are shooting. If you leave it at 12 oclock and are shooting at 3 or 9, or have it set to 3 but are really shooting at 12 or 9, your data is going to be wrong in all directions except the one you trued at. If you use the correct heading when truing, it will track well as you change direction.

2. Scope height is huge. You're probably going to be between 2.2-2.4". If it's set to the default height it's probably wrong, and will skew your data enough to give you a trajectory curve that doesn't match very well.

3. Correct distance is KEY when truing data at distance. If your 500 is really 505, or your 300 is really 297, it's not such a big deal. If your 1000 yard target is really 985 or 1012, that absolutely needs to be input correctly to your solver when you are truing, otherwise it's going to shift the entire trajectory curve and skew the entire thing. 10 yards at 1000 can shift POI by .1 mil or more.

 

[vh20]

Kestrels are terrible about giving you a temp that is too high, which makes your Elev. number go down. Put it in the shade and swing it on a lanyard through the provided lanyard eye to cool it down to the actual ambient temp, then turn the Update in the Environment menu to "No" to lock it in so it won't change. I find just holding it my hand for a minute will cause the Temp reading to rise. If you set it in the sun with the Environment Update on, you can actually watch your Elev. number go down.

 

[vh20]

even the same range me and my buddy were both .4 @ 800 high during sun set...we've shot multiple times in the 30 min- 1 hr earlier time frame and havent had an issue since...the only thing that was different that one evening, was a cold front had come thru, but the sun was out all day...so it was warm during the day, and as the sun set, it went from like 75-80, down into the 50s...not something we can recreate for a while down here since its going to be 85-95 for the next few months im sure

I can recreate this scenario every single day on my range, and I can't really understand it. I'm usually shooting 1000-1500 yards. My dope will always be on in mid-to-late afternoon, but as the sun gets low I will begin to see a weird kind of mirage develop. It's very slow and wavy, like looking at the target through a lazy ripple in water. Also the IPSC targets will take on a square shape, rather than being taller-than-wide as they are. I've come to call it "cooling mirage," a name I made up because it is distinct in appearance from the mirage in the earlier, warmer part of the day, and occurs as the afternoon temps begin to cool with the setting sun. My range is a pretty flat hayfield, so line of sight is just over the top of the ground all the way to the target, and I'm convinced this has something to do with it as well. I tested it once with a tall paper target at 1000. In late afternoon I shot a dead-on group with the dope from the Kestrel to confirm it was correct. Then, as the sun began to set I fired one round every 10 minutes until it began to get dark. I hauled butt to the target to mark each shot with the time stamp, then hauled back to the rifle in time for the next shot. Impacts climbed consistently with each shot up to a peak of about 36 in. (1.0 mil at that distance) over aim point. Just before it got too dark they started to come back down. I still have that paper target rolled up in the shop. This was summer in AL, started shooting around 90 degrees, and temps began to drop slowly to maybe 80-ish by the end - but of course the temp decrease should make the bullet impact LOW, not high. By the way, I shoot due North, so the sun sets on my left, not in front of or behind me.

 

[vh20]

Found some pics. This was the setup. I was wrong about an initial group to confirm dope before the “cooling mirage” began. It was just a single shot, on the right IPSC. Elevation was 8.0 mil, and was not changed throughout the entire test. When the weird mirage first began to develop I switched to the paper target, aim point was the center bull. I forgot to take a pic to begin with, so this was taken after I had already fired two rounds on the paper (ie 20 minutes into the test).

 

[vh20]

Results, every 10 minutes from 1755 to 1900 hours. Also, my phone tells me this was late September, not summer, but still hot down here so that's why I remember it as being summer. But days were getting shorter, so that's why the test ended at only 1900.

 

[vh20]

And I even found my notes from the test. Temps were about 5 degrees less than I said earlier, starting at 85 and ending at 72.

 

[morganlamprecht]

interesting...we saw similar with the "cooling mirage", range is also a long flat sendero cut in a pasture

for both of us, the target would be crystal clear for short periods and then get really hazy/blurry for short periods and it kind of cycled back and forth the whole time

the evening we were both high...we actually continued to shoot past dark with lights on the targets, and we were still high and still had the hazy/mirage issue

even weirder, is when i was at Silent night a few weeks back, my dope was perfect both nights out to 1100 yds or whatever the further target was...no noticeable shift at all

 

[lte82]

we were still high and still had the hazy/mirage issue

Well that might be your problem? LOL

 

[lte82]

The one time I saw a shift that I could verify was not just me, but everyone shooting, was at the Presidents 100 shoot off at Camp Perry a few years ago. Everyone had just come off of the 600 yard line, we waited like an hour or two, then the top 20 shooters got back down to shoot 10 more shots at 600 to determine the winner. Noone changed dope, we literally laid back down 1 hour later and shot the exact same distance in the same wind condition. The only thing that had changed was the sun was headed down and some clouds had come over. Everyones first shot was .4-.6 mil high. You could hear the people watching even sound shocked at what they saw.

 

[vh20]

the evening we were both high...we actually continued to shoot past dark with lights on the targets, and we were still high and still had the hazy/mirage issue

even weirder, is when i was at Silent night a few weeks back, my dope was perfect both nights out to 1100 yds or whatever the further target was...no noticeable shift at all

I've done this as well, with the lights on the targets, on two occasions and experienced the exact same thing. The weird-looking mirage was still there after dark, and the dope was still high. But on these two occasions I didn't start until after dark so I don't know if the impacts were starting to come down from an earlier peak like they did in my twilight test.

 

[Hollywood 6mm]

There's a target at Altus that will screw with you, especially in the winter time due to the light angle. It's most noticble in the winter when the sun is low on the horizon, which puts the sun at about 1-1:30 from the 840/940 yard target - almost directly behind it. That condition will cause you to impact .2-.3 high with any caliber/rifle. I've tested it side by side with a buddy of mine running a 308 when I had my 6 Creed out, and we had the same deflection. Come back to the 700 yard target that isn't in the shade of the trees, and is at a different angle to the sun, and your data is dead on again.

 

[jaybic]

well, I guess that take away from this is for me to pay attention to my zeroing conditions, in detail, and the to note the match conditions and adjust accordingly but only after shooting so I dont assume a change, adjust for it and then find out my dope, in that particular case did not change. I guy could screw himself either way here it seems. Time, wind, sun angle, mirage...am I missing anything else to keep track of? Btw folks, thanks for the help in getting a handle on this.

 

[jaybic]

and keep my kestrel out of my damn pocket..and the sun I guess....

 

[eastexsteve]

The higher the humidity, the more light refraction/distortion you get at long distances. Also, the higher the temperature, the more moisture/humidity the air can hold. Down here in the hot humid south, we deal with it all the time.

 

[Ledzep]

I've tracked roughly 2 MOA worth of image shift on my Nikon D5100 (~10x zoom lens) doing time lapse. In some circumstances with an absolutely fixed 32x rifle scope I've watched the target bounce up and down almost a full mil.

Seems to be related to sunshine as far as I can tell. The entire image grows/shrinks with varying light, but also tracks up & down at the same time. I did one across a valley, about 200 ft above the deck across most of the valley (cliff wall looking at a steep hill) to see if it was mirage off the ground, same results.

Here's the two most extreme examples from the time lapse. Roughly 450 yards.

Have to remember the "invisible lens" that the atmosphere provides between you and what you see. Variable densities cause variable indexes of refraction and light takes the shortest path between two points-- not necessarily a straight line.

Nothing new.. Old timers used to say, "Lights up sights up, lights down sights down", and astronomers never look below ~45 degrees because of all the BS the atmosphere causes.