After a day at he range I had as much as 3/4 MOA drop in elevation at 800 yrds. The morning temperature was in the mid 50's and by afternoon in the mid 70's. Was this drop due to air temp. increase and how can I predict any change in the future? Thanks in advance.
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Range Report MOA shift question.
- Thread starter caseyru67
- Start date
It could have been due to higher barometric pressure, maybe you were getting tired, maybe a combination of those two or more. There could be a number of things going on, sometimes you are the only one that can really answer specific questions.
Mathematics For Precision Shooters
Look at the section, Adjusting for Temperature Changes and Altitude Effects.
Mathematics For Precision Shooters
Look at the section, Adjusting for Temperature Changes and Altitude Effects.
Bear with me for a second! if you are referring to 3/4moa less come-ups on the scope and not 3/4 lower poi on the target. It is directly related to the higher thermals. over a daylong match I will normally lower my scope setting to allow for about 1 moa at 1000 yds. due to higher temps. in the afternoon. This is with Varget powder. with other powders such as Reloader 17 the difference can be even more. If i'm using a summer load in the cold months ( with Reloader 17) I have had as much as 4 moa difference. Powder gives higher pressures on warmer days. I've seen shooters keep their loads in coolers (without ice, of course) just to maintain some degree of consistency all day.
40xs, I dialed 3/4 moa up to stay on target and I was shooting Varget. A data book sounds in order but I would like to be proactive rather that reactive when it comes to predicting bullet path.
That is really the most important reason to keep accurate notes; it allows you to be proactive based on prior experience. The better your notes, the better your chances of knowing exactly how the specific conditions will affect your shot before you even pull the trigger. As an example, if you accurately record drops at various distances across a range of temperatures, you will then have a pretty good idea how a 30 degree temp differential will affect your POI. It is not at all uncommon to see temperature changes of 30 degrees between the first and last matches of the day out here in San Diego, particularly in spring/fall. For me, that usually means 0.250-0.375 MOA (1-3 clicks) down elevation at 1000 yd as the day warms up. The same holds true for pretty much any other atmospheric variable that might affect your shot. The more you know from past experience, the better prepared you will be for the next shot. I have also found that keeping accurate notes has prompted me to learn more about the specific variables I need to be thinking about and how they will affect trajectory. This is also proactive as the better you understand that factors that influence external ballistics, the better prepared you will be to make the correct adjustments for a specific set of conditions. Bottom line, keeping good notes can be a very useful tool. Best of luck with your shooting.
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Deleted member 10043
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It doesn't really matter that it dropped. Well, it does and it doesn't. At the time trust your bullet and then go back later and figure it out. Is this a known range spot? I have one known range [MENTION=80736]500[/MENTION] meters that messes with our scoring. Half the time it is 1MOA lower than anticipated because of a series of adjacent berms and natural hump in the land about half way down range that brings the bullet closer to the ground for about 100 meters. It can occur in cold and hot weather. I love that range. Everything is a factor down to powder temp to stay on target throughout the day.
