Effects of head wind on bullet drop

[Snakeoil]

Yeah, I know, the general consensus amongst the shooting writers is that headwinds have little to no effect on bullet path. I did not subscribe to that opinion, but read it enough that I figured that smarter folks than me came to that conclusion. But today, I was writing up a guide for reading the wind for the guys at Wilton and it was all driven by the experience I shared earlier today regarding headwinds creating vertical crosswinds due to berm between the shooter and the target. As I was writing, I decided to take a harder look before I repeated the accepted axiom. I went to Shooterscalculator.com and ran the numbers for the same bullet at reduced load velocities. What I found was that if you took a given wind, in this case 30 mph and used the wind speed to either increase or decrease the friction effect on the bullet, it resulted in about a 2 MOA difference in bullet drop at 500 yds. That could be the difference between a hit or a miss.

I ran the same bullet at 2500 fps and the drop reduced down to just under 1 MOA. This lead me to believe that the writers are using modern HV rifle ammo as their point of reference when they say that headwinds have no appreciable effect. I have come to the new conclusion that for reduced loads that push a 200 gr bullet at about 1500 fps or less, head winds make a difference and need to be considered when picking a point of aim at extended yardages.

 

[RicinYakima]

I agree 100% Rob. I shot Military rifle cast bullets (.30 caliber 220 grains at 1450 f/s) for 20 years and head and tail winds are noticeable. Especially if you are shooting over berms at 50, 100 and 200 yards.

 

[Snakeoil]

I agree 100% Rob. I shot Military rifle cast bullets (.30 caliber 220 grains at 1450 f/s) for 20 years and head and tail winds are noticeable. Especially if you are shooting over berms at 50, 100 and 200 yards.

The berms raise a separate issue. The tech writers all call out those effects in that obstructions like walls and berms turn head and tail winds into vertical cross winds with the same effects. I'm talking about pure head and tail winds.

I sent my Reading the Wind write up to several guys at Wilton to get their input. I use the experienced shooters as my editors and critics. If something is not clear to them, it sure won't be clear to a newbie or less experienced shooter. When I get the write-up finalized, I'll share it here. Might help someone who is struggling to understand what is going on after the bullet leaves the muzzle.

 

[RicinYakima]

The berms raise a separate issue. The tech writers all call out those effects in that obstructions like walls and berms turn head and tail winds into vertical cross winds with the effects. I'm talking about pure head and tail winds.

OK, stop reading at the end of the first sentence.

 

[fiver]

so anything about nose up over spun bullets?

 

[Missionary]

Well this will be an interesting read. Another technical thesis that reminds me I should always be aware that if I miss it was another unforeseen factor.
Oh the present joys of hunting about the river bottoms... Only concern we have is that ever present twig nudging a shaft enough so Mr. Groundhog does not get ventilated away from the main thwaping area.

 

[Snakeoil]

so anything about nose up over spun bullets?

I'm not sure what you mean.

 

[popper]

Of course headwind has an effect on POI. BC and time to target. Read the code for the ballistic calc and you see it. Just like crosswind. I doubt many hunters actually shoot when wind speed is 30 mph+. Yup, shoot a high BC bullet at HV and drop is minor at CLOSE range.

 

[Michael]

For some real fun, make it a fishtailing head or even a tail wind.

 

[Snakeoil]

For some real fun, make it a fishtailing head or even a tail wind.

You know, I've never heard it described using that phrase. But an article I found also talked about fishtail winds. The article confirmed my thoughts on what is going on and went further to demonstrate why a fishtailing headwind plays more havoc than a changing crosswind. Here's a link in case anyone is interested.

Why Headwinds are More Difficult than Crosswinds

How shooting in a crosswind is different than shooting in a headwind.

bisonballistics.com

 

[Mainiac]

When i was shooting br,,if i had to shoot head winds,i knew i was gonna lose x,s high,,so hold low.

 

[popper]

He is kinda right. There are 2 vectors, bullet trajectory and wind 'trajectory'. Head/tail add directly the the bullet effective fps. 30 mph wind is 45 fps. That equals 45 SD! Makes a difference @ 1k yds. The effective vector at the bullet is larger for a headwind. But the exposed amount (part that wind works on) of bullet is LESS than for a crosswind. Gyro effect can be a bigger factor - kick it off axis much and it wants to go 90 deg. That part is FUN!! Bullet vector doesn't change along the path much (corolious effect) and spin stability.

 

[Snakeoil]

One of the challenges at Wilton is the range is surrounded by very tall pines and so are the tops of the BPCR berms that are staggered along the right side of the range with the 500 yd berm making the end of the entire range. So, when the wind blows, it takes various paths, creates eddies and so forth. We also shoot from a covered firing line. If there is a tail wind, it blows over the roof of the firing line and makes for some interesting wind currents that are quite obvious when a BP round is fired. We've seen the smoke go straight up and straight down as well as sit right in one spot and spin. Never a dull moment trying to figure out what is going on for the next shot.