Well, I went and joined the AR brotherhood - got the M&P Sport. Weather and work have prevented me from taking it out the range, but I may finally get a chance this Monday to get in some shooting. I'm planning on doing some sighting in, get a general feel for it. I'm still learning this platform, and was wondering at what point does wind play a factor in assessing accuracy - at what speed does it become a factor, if at all? It might be windy here, and I don't want to make a misinformed judgment on how well it's shooting for me based on that. I've shot .22LR long gun ( a Marlin 795 ), so I know wind can be a factor - but how different is it for .223/5.56?
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Trying out my new AR - wind question
- Thread starter steelbird
- Start date
It largely depends on the bullet's ballistic coefficient but also depends how long the bullet is being pushed by the wind and how strong the wind is. Meaning if you shot the same bullet at 2000fps then 4000fps, the faster one would have less drift over a given range compared to the slower one.
Use a ballistic calculator that accounts for wind to get a better idea on how wind will effect the bullet's flight.
In a 10mph 90 degree crosswind you're looking at about 1-2 inches of drift(with .223/5.56), depending on the bullet's BC. The higher the BC the less the wind will affect the bullet's flight, and on top of that, they will lose less velocity over a given range compared to a lower BC bullet. To give you an idea, a typical 9mm 124 grain bullet would have close to half a foot of wind drift, in the same conditions.
Use a ballistic calculator that accounts for wind to get a better idea on how wind will effect the bullet's flight.
In a 10mph 90 degree crosswind you're looking at about 1-2 inches of drift(with .223/5.56), depending on the bullet's BC. The higher the BC the less the wind will affect the bullet's flight, and on top of that, they will lose less velocity over a given range compared to a lower BC bullet. To give you an idea, a typical 9mm 124 grain bullet would have close to half a foot of wind drift, in the same conditions.
.223 drifts significantly less than .22LR because you're generally shooting spizters in the .223 and round nose in the .22LR. This gives the .223 higher BC bullets, in general. It also gets shot at roughly 3x the velocity. So less time of flight to the target means less time in the wind. At 100 yards .223 has roughly .1 seconds time of flight. .22LR takes .32 seconds to reach that same 100 yard mark. That being said, .224 cal bullets generally don't have incredibly high BC bullets... Not when you compare them to heavy 6.5mm, 6.8mm, 7mm, .308, .338, .50 cal projectiles at least. So they can get pushed around in the wind a bit. No where near as bad as .22LR, though.but how different is it for .223/5.56?
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use JBM Ballistics to print out a ballistics chart for your particular load.
A "British Wind Chart" will get you started with most service rifle loads.
10 mph wind, full value (90 degrees)
100 yards, 1 MOA
200 yards, 2 MOA
300 yards, 3 MOA
400 yards, 4 MOA
500 yards, 5 MOA
Hope this helps.
Jimro
A "British Wind Chart" will get you started with most service rifle loads.
10 mph wind, full value (90 degrees)
100 yards, 1 MOA
200 yards, 2 MOA
300 yards, 3 MOA
400 yards, 4 MOA
500 yards, 5 MOA
Hope this helps.
Jimro
Art Eatman
Staff in Memoriam
Not a bad chart. On a prairie dog hunt where I figured the wind somewhere over ten mph but under twenty, I was getting around five to six inches of drift at 300 yards, crosswind.
Open sights or scope? With open sights the wind drift my be blurred by group size.
Last weekend, we did some initial sight in of a couple of ARs for my son-in-law. His groups with open sights were large enough that the 20mph crosswind made little difference.
If I have to do a scope check or sightin during high crosswinds, I usually make allowance for 1-1.5" of wind effect. Usually good enough for most hunting uses. My range is between two hills which has a buffering effect unless the wind is directly from the east or west.
Last weekend, we did some initial sight in of a couple of ARs for my son-in-law. His groups with open sights were large enough that the 20mph crosswind made little difference.
If I have to do a scope check or sightin during high crosswinds, I usually make allowance for 1-1.5" of wind effect. Usually good enough for most hunting uses. My range is between two hills which has a buffering effect unless the wind is directly from the east or west.