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Author Topic: Wind speed and bullet drift  (Read 286 times))

Online Spacebus

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Wind speed and bullet drift
« on: April 24, 2022, 05:57:49 PM »
I live on the coast and our winds are variable and can come from any direction. Today the weather folks said the wind was around 10 MPH, but I tried to time shots between gusts/breezes. At what wind speed do lighter slugs start to become inaccurate? I would have assumed a .25 cal 42-FN BBT at 850-900 FPS or .249-39 HP traveling 900-950 FPS would have less wind drift or stability issues, but I saw it first hand. I tried shooting at 50 yard but could not keep a group in a 4" circle. At 25 yards groups were still going from 1/2" up to 2". All of my shots were from a heavy bag under the rifle on a table seated. Unfortunately my chronograph isn't working right now and I'm waiting on a new one, so I can't give 100% accurate data.

Would a 200+ FPE .257 resist wind better? My .457 Challenger shooting 225 grain HP BBT (.458-244-FN) at 960 fps can keep five shots touching at 50 yards.

I suspect my powdercoat skills may have contributed to some of the group size issues on the .249-39 slugs, but the BBT's could group in 1/2" at 25 yards no problem.
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Offline rsterne

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Re: Wind speed and bullet drift
« Reply #1 on: April 24, 2022, 06:16:00 PM »
Drift is proportional to the crosswind speed (vector at 90 deg. to bullet path), and to the BC....

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Offline A moron

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Re: Wind speed and bullet drift
« Reply #2 on: April 24, 2022, 06:24:55 PM »
I have a hard time with it .

Shooting opensighted  i shoot dead on to see whete i hit then walk back and apply Kentucky windage the best i can.

Not a clean target but slapped a snuff can lid on a cleaner spot on the cardboard shot and was low right  about 4 oclock or so. Then shot about on that scribble in spot  the best i could at 11 to clock and was able to at least get in the lid each time ..lol...

Man im sick of this wind here  everyday for months now. Like 10+.

Kinda sloppy picture to look at 

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Offline rkr

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Re: Wind speed and bullet drift
« Reply #3 on: April 26, 2022, 12:58:39 AM »
I have only 160 fpe .257, but it has less wind drift than a .22lr at 100m. In bad wind conditions groups spread out to 1.5"-2" at 100m.
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Online Spacebus

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Re: Wind speed and bullet drift
« Reply #4 on: April 26, 2022, 08:20:59 AM »
I have only 160 fpe .257, but it has less wind drift than a .22lr at 100m. In bad wind conditions groups spread out to 1.5"-2" at 100m.

Do you know how .257 compares to .308 for air guns? That's the kind of performance I am looking for at long range. Are you using cast slugs?
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Offline rkr

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Re: Wind speed and bullet drift
« Reply #5 on: April 26, 2022, 08:35:10 AM »
I have only 160 fpe .257, but it has less wind drift than a .22lr at 100m. In bad wind conditions groups spread out to 1.5"-2" at 100m.

Do you know how .257 compares to .308 for air guns? That's the kind of performance I am looking for at long range. Are you using cast slugs?

.257 is about the sweet spot for good BC bullets shot at reasonable pressure. .308 has better bullets but to get them up to speed means you need more than 3000 psi with 30" barrel. I'm shooting cast 257420BTs from my gun, best 5 shot group so far is 12.5mm at 100M. I was last weekend at range in a bad weather shooting my .257 and Anschutz 54 and .257 did better groups.
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Huub Viking Mk2 .177/.22 bullpup - grab'n go gun
BSA Scorpion SE .177 - 12 fpe UK model
BSA Scorpion .25 - 100M BR gun at 60 fpe
BSA Scorpion .224 - 100M BR gun at 100 fpe
Evanix Blizzard .257/.357 - 160/230 fpe
Exanix Sniper X2 .357/.45 - 210/270 fpe silhouette gun
Drozd Blackbird HPA - 1200 rpm full auto fun gun / meat grinder
Evanix AR6 carbine/pistol
+ a couple of springers

Online Spacebus

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Re: Wind speed and bullet drift
« Reply #6 on: April 26, 2022, 09:48:01 AM »
I have only 160 fpe .257, but it has less wind drift than a .22lr at 100m. In bad wind conditions groups spread out to 1.5"-2" at 100m.

Do you know how .257 compares to .308 for air guns? That's the kind of performance I am looking for at long range. Are you using cast slugs?

.257 is about the sweet spot for good BC bullets shot at reasonable pressure. .308 has better bullets but to get them up to speed means you need more than 3000 psi with 30" barrel. I'm shooting cast 257420BTs from my gun, best 5 shot group so far is 12.5mm at 100M. I was last weekend at range in a bad weather shooting my .257 and Anschutz 54 and .257 did better groups.

I appreciate you sharing your experience. I live in such a windy place I'm learning that if I want to shoot past 25 yards my Eagle Claw and Stormrider are not cutting it. On a perfectly calm day I can get good accuracy at 50 yards with both, but we normally have a 13-20 KPH wind. My .45 cal rifle doesn't seem to care about wind at 50 yards, but It's pretty hungry for air.
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Crosman 362 #785
"Mike Tuned" Ruger Airhawk .177
Chiana Bandito .22 regulated
SPA PR900W .22 regulated
Daisy 901
Seneca Eagle Claw .25 (75.6 FPE 43.5 NSA)
A.E.A. .45 Bullpup (500 FPE 305g NSA 860 FPS)
Yong Heng & Hatsan 1.6l bottle