http://www.gunsmoke.com/guns/1022/22drift_cross.html
The thing is that drift isn't determined by the time of flight. It's related to the "delay" time, i.e. the time between when the bullet arrives in a vacuum versus the time that it actually took in air.
The HV round while having a shorter time of flight, has a greater delay...more wind drift.
If you are interested, PM me an e-mail addy, and I can send a reasonably rough "stepwise" spreadsheet .22 model.
Hot water freezes faster than cold water?
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Rounds going subsonic while in flight can be a problem, which is why heavier, longer bullets are often used at longer ranges. This is a bit of an issue with either the .308 or 30.06 at 1000 yds. An example would be the 173gr FMJ BT match bullet for either, where being subsonic at 1000 yds would be about 1100 fps, which is similar to a heavy load in a .357 mag at the muzzle.
Must be getting disoriented while passing through Mach 1, ending up with more drag than the subsonic, for the rest of the trip.
The super/subsonic thing for rimfires over accentuates the issue.
A light (bad BC) bullet at a high velocity will often fair worse than a heavy (good BC) at a lower velocity, as the lag time is/can be greater.
Remember that the CD above the speed of sound is around 5 times that below...excluding the funny business that happens trans-sonic.
I'm still trying to get my brain wrapped around this "lag time" concept.
Back in the 50's, we understood speed of sound issues. I had a reloader make up some 30-06 225 gr. solid lead rounds to shoot at ~1100 fps. Was an interesting experiment. Was too expensive for me continue at the time.
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Not knowing a thing about the whole velocity topic ..
Shannow says that supersonic velocity has a higher vacuum to atmospheric ratio of "loss".
Subsonic is a lower vacuum to atmospheric ratio of "loss".
Therefore atmospheric influences impact super sonic more.
Is that about it?
Yup. That's the "lag time" thing. I'm still trying to get it straight in my head. I think I may have a terminology problem, rather then a technical problem. I don't understand what a vacuum has to do with it, but I'll figure it out.
Wish there was a whiteboard here.
Scenario 1, shooting a target from a moving platform in a vacuum.
Bullet leaves the muzzle with an X and Y velocity, hits the target in T seconds, missing the point of aim by TxY
Scenario 2, same test in an atmosphere. Bullet has an X and Y velocity, and is slowed equally in both directions, as it's movement is the vector sum of the velocities. Hits the same point (albeit lower) than Scenario 1, i.e. TxY
Scenario 3, shooting from a stationary platform at a moving target in a vacuum. Bullet only has X velocity, target Y right angles to it. Bullet misses centre by YxT again, same as 1.
Scenario 4, same as 3, but with an atmosphere. Bullet has X velocity, target Y. Bullet is dragged, only in the X plane, leading the time of flight to be T+t. Misses centre by Y*(T+t).
t is the "delay", "lag" whatever terminolgy you need.
Scenario 5, shooting from a moving platform at a moving target. Is a superposition of scenario 2 and 4, so the bullet misses the centre by Y*(T+t)-Y*T, or Yt - the miss is related to the "delay", and the speed of the moving platform and targets, no the absolute velocity.
Scenario 6, stationary target and platform, and move the air between them at the same velocity as the elements moved in 5. Result is the same as 5, with the miss being related to the delay, not the absolute velocity.
In the case of a supersonic .22, the 1200fps projectile gets there quicker, but is delayed more than the subsonic, leading to higher drift.
This holds up to .22 magnum velocities, when everything starts to catch back up.
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Scenario 2, same test in an atmosphere. Bullet has an X and Y velocity, and is slowed equally in both directions, as it's movement is the vector sum of the velocities. Hits the same point (albeit lower) than Scenario 1, i.e. TxY
Taking into account the BC of the bullet profile in both directions of course... 
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Wish there was a whiteboard here.
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In the case of a supersonic .22, the 1200fps projectile gets there quicker, but is delayed more than the subsonic, leading to higher drift.
Close I think.
Look at the current winchester page
1065 fps muzzle, 922fps @ 100 yards, lost 143fps (13.4%)
1150 fps muzzle, 976fps @ 100 yards, lost 174fps (15.1%)
1255 fps muzzle, 1017fps @ 100 yards, lost 238fps (19.0%)
1300 fps muzzle, 1038fps @ 100 yards, lost 262fps (20.2%)
magnum
1550 fps muzzle, 1147fps @ 100 yards, lost 403fps (26.0%)
2120 fps muzzle, 1435fps @ 100 yards, lost 685fps (32.3%)
Ok but why does the greater percentage of velocity loss account for greater wind drift?
The higher speed will encounter much higher drag due to the "squaring" of the resistance so a greater loss is expected (all else being equal).
Go back to my whiteboard.
The drift isn't related to the total travel time, but how "late" the projectile is.
Here's the results of my ballistics model, using a 40gr lead projectile at various speeds. The model uses straight drag, against the true direction of the projectile (vector sum of the wind and longitudinal components).
Note, it's an "all else being equal" model, and you'd never be trying to send a low Ballistic Coefficient round nose lead projectile at 2650 fps. Range 90m (100 yards) Delay is in seconds, drift in inches. Crosswind 5m/s (11MPH)
The projectiles that you would be using are far better.
It's the minimisation of "delay" that makes better BC projectiles less affected by wind, while it is lower time of flight that affects the vertical trajectory.
Note, it's an "all else being equal" model, and you'd never be trying to send a low Ballistic Coefficient round nose lead projectile at 2650 fps. Range 90m (100 yards) Delay is in seconds, drift in inches. Crosswind 5m/s (11MPH)
The projectiles that you would be using are far better.
It's the minimisation of "delay" that makes better BC projectiles less affected by wind, while it is lower time of flight that affects the vertical trajectory. Quote:
In a nutshell then, we see that wind drift can be minimised by increasing speed or increasing BC. First prize is if one can increase both. With these facts at hand, let us look at some practical examples. On a recent springbuck hunt, a variety of calibres and bullets were used. On one of the days of the hunt, we had strong wind to contend with. The figures are given in table 4 for a 40km/h wind with three of the calibers used on the day. None of these bullets are shining examples of high BC numbers and especially the .224 would normally be assumed to be a real dog in the wind. It had a lot of speed going for it though, and performed well. The bullets used were: 40gr HV bullet in the 22x64, 139gr flat nosed jacketed lead bullet in the 7-08 and a round nosed flat base jacketed lead bullet in the 30-06.
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The actual mechanism of wind drift is interesting as it is often assumed that it is the result of wind blowing on the side of the bullet. In reality the bullet vectors (turns) into the wind within a short distance after exiting the muzzle. The stronger the wind, the more acute the angle the bullet assumes into the wind. The result is that the drag on the base of the bullet is then offset more to the downwind side of the bullet path and drags the bullet in that direction. More on this subject can be seen here.
Based on the premise that an increase in speed as well as BC can only be beneficial in reducing wind drift, a practical comparison of the advantage of HV bullets is given in table 5. The caliber is 30-06 and the comparison is made between a 150 gr HV bullet, a jacketed lead 150 gr bullet and a 180 gr jacketed bullet at typical speeds for these bullets. Wind speed is taken at 25 km/h.
http://www.gsgroup.co.za/winddrift.html
Yep, that's exactly how it works, and how I modelled it.
It's just the range of velocities that .22s work in is the just supersonic range.
The examples that you are showing are quite supersonic.
Look at my curves past 1700 fps...more speed less drift.
But the drift is related to the delay, NOT the absolute velocity.
OK, seeing as we can only trust links and other people's work.
(He does give the formula better than me, but I like my whiteboard approach better - if there's a whiteboard)
Note T-Tv = delay
http://www.airgunbbs.com/forums/archive/index.php/t-239598.html
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Wind deflection is well understood by bullet manufacturers and the military as they have both done extensive research on this subject since firearms were invented.
One of the calculations used for wind deflection is Didion's Formula. This calculation has been proven to be spot on over years of use at the US military Aberdeen Proving Ground.
The equation for a 90 degree crosswind is as follows:
D = (W*(T-Tv))*12
Where:
D = Bullet displacement in inches
W = Crosswind velocity in fps (not MPH!)
T = Actual bullet flight time in seconds
Tv = Theoretical bullet flight time in a vacuum in seconds (=distance(feet) over muzzle velocity(fps))
For example, if we take a .22 LR bullet with a MV of 1085 fps over 200 yards with a flight time of 0.6316 seconds and a 10 mph crosswind, the formula is:
D=(14.67*(0.6316-0.5530))*12
= 13.8"
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OK, seeing as we can only trust links and other people's work.
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In a nutshell then, we see that wind drift can be minimised by increasing speed or increasing BC. First prize is if one can increase both.
So the sideways wind vector is also considered to be supersonic, and thus puts more force on the projectile?
Ok, I can relate to this. When I was flying, in order to get from point A to point B, I had to calcuate my heading to account for the wind in order to maintain a flight path. The advent of cheap handheld GPS units made it much easier to maintain the true flight path.
substitute an outline of an airplane for the bullet and it all becomes clear.
I still don't understand the term "delay time" but I think we are talking about the same thing.
Thanks Tempest. Good stuff..- Status
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