Which would take the less wind?

[averageplinker]

Ok, before I pose the question fully I want to point out that I know many, many factors/variables will come into play and wish to avoid lots of replies noting "have you/you haven't taken this, that or the other into account". I will even suggest an answer format that will remove the temptation to reply more fully

If a .177" pellet and a .22" pellet of the same design were both fired at sub-fac power (let's say 11ftlbs) at the same time at the same target which would be less affected by wind drift?

If it helps please free to limit your answers to noting the calibre that you believe will take less wind and whether your view is from experience, ballistic modelling, guesswork or received wisdom?

Cheers Rich

[Ragle Jnr]

I used to think the heavier 0.22 was less effected, but have come to realise that the bigger cross section and slower pellet speed means that wind has more effect on the larger caliber. Think LGV compared to car in cross wind. David. No I haven't tried comparative testing!

[BTDT]

Think LGV compared to car in cross wind. David. No I haven't tried comparative testing!

Unlike the LGV and car, the wind does not blow against the side of the pellet.

[averageplinker]

I was initially confused by mention of the LGV, thinking what has a Walther rifle got to do with it?

[averageplinker]

Unlike the LGV and car, the wind does not blow against the side of the pellet.

Wow, that sounds almost mystical. Am I your Grasshopper and you are my Master Po?

BTDT, do you have a view on which would take less wind? Apologies if you have covered it in a magazine article I have not read.
Cheers

[Ragle Jnr]

The spinning pellet will act like a helicopter rotor, there will be an advancing side, adding to wind speed, and a retreating side, subtracting from wind speed, this will create uneven forces, much as shooting through rain!
BTDT, how does the wind not affect the side of the pellet? I presumed the OP referred to cross winds, but even shooting into head and tail winds alters POI. David

[BTDT]

The pellet steers into what it sees as a single air flow. Air molecules either hit the front, or pass by the side.

Where's Ballisticboy when you need him?

A short cut to the original question, If you multiply the muzzle velocity by the ballistic coefficient, whichever pellet gives the highest result will be the least affected by wind drift.

[averageplinker]

Ah, we are getting more complex (just as I suspected we would). I was hoping for a general rule of thumb to use as a starting point. Any takers?
Cheers Rich

[GPConway]

The extent of Lateral drift depends mostly on Muzzle Velocity and the projectile's Ballistic Coefficient / Drag Law. Note that this doesn't depend directly on either the calibre or the projectile weight ... although - indirectly - the Ballistic Coefficient of course depends on both.

e.g. this for the Lateral Drift at 50 Yard under the influence of a 5 MPH crosswind v. various muzzle velocities.





Obviously, this is derived analytically.

George

[GPConway]

... A short cut to the original question, If you multiply the muzzle velocity by the ballistic coefficient, whichever pellet gives the highest result will be the least affected by wind drift.

True enough if the projectiles all have the same Drag Law and form factor; otherwise you're comparing apples with oranges and the results might be confusing or just plain wrong.

It doesn't help to determine the extent of the drift though. For that it all gets a bit more involved ...

George

[PCPShooter]

In 'my mind' if nowhere else , 177 heavies seem a bit less blown of course by wind ...
Well I might shoot in a gentle breeze, not even a wind really - if target shooting there is no risk of causing suffering .

[RobF]

The spinning pellet will act like a helicopter rotor, there will be an advancing side, adding to wind speed, and a retreating side, subtracting from wind speed, this will create uneven forces, much as shooting through rain!
BTDT, how does the wind not affect the side of the pellet? I presumed the OP referred to cross winds, but even shooting into head and tail winds alters POI. David

Only by tiny amounts.

5 mph head wind is less than 1% of a pellet's speed at 800 fps, or about 7 fps. So you'd see more effect from just shot to shot variation than you would 5 mph.

Typically shooters vastly over estimate wind speed. They assume that the weather prediction relates to wind at ground level. In reality it doesn't, it's supposed to be a 10m high post in a 100m radius empty flat area. Typically ground speeds are in the order of 1/3-5th of what they are predicted to be by the weather prediction. So if you look up the weather and see that it's 5-10mph you're likely to be shooting in 1-2-3 mph maybe.

[averageplinker]

If it helps to know what I want to do, ergo why I am asking.........the club I shoot at has a 50yd bench rest competition which I will have a go at this year. The object is to take 5 shots, the smaller the grouping the better the score. So I am wondering whether to use a. 177" with heavier pellets or a .22" with medium pellets (i.e.using what I have available without buying a whole new rig etc).
My inclination is to go with .177" heavies but I idly wondered if a .22" might deflect less in the wind. If I can't get a rough idea here i will go for .177" to start off (and if I can find the time do some back to back testing of both calibres outside of the comp).
Rich.

[BTDT]

True enough if the projectiles all have the same Drag Law and form factor; otherwise you're comparing apples with oranges and the results might be confusing or just plain wrong.

It doesn't help to determine the extent of the drift though. For that it all gets a bit more involved ...

George

I can't argue with that, George, but with the two pellets of the same design at 11 ft. lb. as mentioned in the OP, I think there's a good chance Ballisticboy's BC x MV will be a fairly good guide.

[GPConway]

In 'my mind' if nowhere else , 177 heavies seem a bit less blown of course by wind ...

Not only in 'your mind' but in reality too but the difference is due to the change in the Ballistic Coefficient caused (indirectly) by the difference in weight ... given that the same Drag Law and Form Factors are applicable.

i.e.,

Given that the 8.44 Grain 0.177 JSB Exact has BC[GA2] = 0.0195 ... and assuming that the same Drag Law (GA2) is appropriate in all cases ...
for the 7.89 Grain JSB Express: BC[GA2] = 0.0195 * 7.89 / 8.44 = 0.0182 and,
for the 10.34 Grain JSB Exact Heavy: BC[GA2] = 0.0195 * 10.34 / 8.44 = 0.0239

At their respective Muzzle velocities (for 11.0 Ft･Lbf muzzle energy) the Lateral Drift at 50 Yards and a 5 MPH crosswind are ...

JSB Express: 792 Ft/s, 2.92" drift
JSB Exact: 767 Ft/s, 2.78" drift
JSB Express: 692 Ft/s, 2.37" drift

I can't argue with that, George, but with the two pellets of the same design at 11 ft. lb. as mentioned in the OP, I think there's a good chance Ballisticboy's BC x MV will be a fairly good guide.

Absolutely! I was just trying to emphasize the fact that you need to be careful with the Drag Law assumptions.

George