Henry Rifle Forums

Currently we are having high humidity and smoke. It got me wondering if it would make a measurable drop in 200 yards. Would the type of bullet matter?

In my experience, yes, air density has an effect on bullet drop and humidity is part of that density. However, it is important to note that dry air is actually heavier than wet air, because water vapor molecules are actually lighter than oxygen and nitrogen molecules, meaning that in damp air, the lighter water vapor molecules are are a larger percentage of the density. The tricky part is separating the effects of humidity and smoke from all the other air phenomena that take place along with it. Humidity often acts in concert with other air factors.

Interesting topic, though. About 5 years, back, I spent a summer shooting my air guns at 50 yards to establish a baseline for air gun accuracy. Light 8 grain 177 pellets are notoriously vulnerable to air currents and wind, as I quickly discovered and this really shows up at 50 yards. I also discovered that even humidity at that distance made a difference. I did see POI shifts between muggy days and dry days at that distance, but that could have just as well have been a matter of changes in air stability over the course of the pellet traveling 50 yards.

I even placed homemade wind flags at 10 yard intervals and on some days I was amazed at how differently those 5 flags behaved, even though I was feeling no effects from the wind at all. Some calm wind days are not as calm as we might believe. I even noticed that days where the air produced a lot of mirage in the scope were less favorable for accuracy.

JBM Ballistics can give you that answer. How precise that answer is depends on how precise your actual inputs are (MV, etc.). GIGO.

http://www.jbmballistics.com/ballistics ... tors.shtml