Environmental causing crazy amounts of vertical



  • Shot a match yesterday and was shooting really good all day should have placed in the top 5. We had two stages that something strange was going on. In the first stage both our RO’s and one other shooter hit 1 mil high at 747 yards resulting in 2 0’s and a 1 for that stage, every other shooter in the squad including myself did not have any issues, the very next stage was the exact same yardage in fact the targets were right beside the previous stages target. It was a tower stage so the RO’s and 4 shooters went up at the same time. The first two shooters that shot did very well one cleaned the stage and another dropped 1 point. The other two shooters and both RO’s where back to hitting 1 mil high. I went up with the second group of shooters and I was first to shoot, same dope as the previous stage and every round was high right at 1 mil, that stage ended up costing me dearly and I walked off with a 0. After the stage was over me and the two RO’s shot again just to try and figure out what was going on. Me and the first RO were still 1 mil high but on the first RO’s last shot after coming down almost a full mil the last shot dropped low by damn near a mil. The second RO seeing that said I’m gonna try my original dope and see what happens, he fired one shot and center punched the target when that same dope had been 1 mil high during his stage.
    The wind was around 7 mph left the right at roughly our 10:00, and it was overcast with a light rain so mirage was not an issue. Me nor anyone else had any idea what caused this massive amount of vertical shift for those two stages but it got quite a few people through the day there with many of them being very experienced shooters.

    Any ideas what could have caused this? @orkan I figure if anyone here knows and is capable of explaining it it’s you.



  • Here's some possibilities. Perhaps not one by itself, but if they stack, for absolutely certain can it create a mil at 750.

    Things that can easily create a mil of elevation at 750yds:

    1. If you were right on the edge of a node, with temp sensitive components.
    2. If there was a 3:00 wind of appreciable velocity.
    3. If the shooters firing position was weak in the rear support and/or hard in the front.
    4. If the shooters NPA was out of alignment due to improperly built firing position.
    5. If the target was up or down angle.
    6. If there was deceptive lighting on the target, either due to light itself or mirage.
    7. Countless more subtle variables.

    Numbers 3, 4, and 5 can cause it all by themselves individually with no help from any others.

    Number 3 and 4 can be eliminated as a possibility by any student that has attended training here, and can self diagnose.

    If the wind is strong enough, you can assign as much as a half mil to #2. You can easily assign another 0.2-0.4 mils to #1 depending on components, conditions, and other variables.

    Numbers 6 and 7 can EASILY assign a half mil of the blame, depending on the conditions.

    So it's not hard to imagine a stage where some shooters simply neglect to address all of the appropriate variables which lead to a mil of undesirable POI. Have a look at the 100yd playing card shots for the atlas bipods that you see at matches. Some dudes legit can't even land one on their own card... and that's a straight up prone 100yd shot. Those are often the same guys claiming all you need to win a match is a 1moa rifle. ;)

    Not saying this describes you. I'm simply saying there are too many variables for me to list here which could easily cause a shooter or shooters to miss by a mil at 750yds. It's also not improbable that several shooters would do the same thing and achieve similar results.



  • @bull81 said in Environmental causing crazy amounts of vertical:

    The wind was around 7 mph left the right at roughly our 10:00, and it was overcast with a light rain so mirage was not an issue.

    Shooting in the rain can fool you with variable lighting and multiple wind shifts even across seemingly uniform terrain. It is hard to know the true depth and density of clouds above the range when the ceiling is low and cloud cover seems fairly uniform from the ground. Cloud depth affects air temperature/density/wind velocity. Unlike heat shimmer in the mirage we all know and hate, variation in air density due to moisture content is likely to be relatively stable, thus undetected, but it will still affect the apparent position of a target. Bands of rain density create just as much mirage effect as hot ground does and it can change rapidly depending on cloud density and cloud depth. Wish I could tell you how to dope this effect but I haven't figured out how to dope for conditions I can't see through a spotting scope.



  • The biggest problem with rain is wet ammo/chambers.

    This will create a massive pressure spike and will undoubtedly send rounds high.



  • I’m thinking it was something related to the lightning and the environment , both stages were shot prone, one from a wooden pick nick table and the other from a wooden tower so the shooting positions were basically identical. All the stages were shot from under cover so wet chambers/ammo weren’t an issue this particular time. It was nice not to have all your gear soaked by the end of the match.

    I wish there was a way to know for sure what caused and how to read those conditions in the future. I’ve never seen anything this drastic before. Most likely like @orkan said it was several things stakes up at once



  • The last match I shot at, we had targets out to 995yds. Some guys got skunked by the variable winds which surprisingly caused a lot of vertical, but after reading about aerodynamic jump or gyroscopic precession, it made sense. I got skunked on a stage where the wind was coming 3:00 10-15mph and I was hitting 2moa high, so I dropped 2 moa in my reticle and let one go just as the wind shifted and hit right. I played that game for 9 rounds lol. Some of the more experienced guys would see their splash, adjust and let 3-4 rounds go in a couple seconds, then wait for the wind to change and do it all over again. Shooting PRS matches has really opened my eyes!