Wind drift question

[harrymoreland]

Take two pellets, shoot them from the same (type of) gun/barrel with the same cross wind (10mph?)

JSB .22 25.,39 at 970fps(ish)

JSB .25 33.95 at 870fps(ish)

Which will buck the wind better?, why, and by (roughly) how much.

Real world input, computer calculation and educated guesses welcome

Thanks.

 

[theLBC]

https://hardairmagazine.com/ham-columns/the-external-ballistics-of-diabolo-pellets/

 

[18.13]

At 50yrds the heavy gets pushed 1.08 in the 25.4 gets pushed 1.33inches because the heavy has a higher BC

 

[Centercut]

About the same. The BC for the .22 RD Monster and the .25 Heavy Mk2 are very close. The original .25 King Heavy had a higher BC but they are no longer produced (they worked way too accurately in the polygonal barreled guns so JSB of course had to change them and no longer produce the successful ones). As a side note, throw in the .30 JSB Exact 44.74, and it will drift MORE than either of the two above since it has a lower BC.

 

[theLBC]

there seems to be a velocity sweet spot, per ham.

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[dizzums]

not enough to worry about .. the drop from the heavier pellet will be a much larger concern ..

 

[Centercut]

If you are target shooting with known distances the drop is inconsequential. If hunting where you might have to guess then it could make a difference... The drop differences aren't huge when you get right down to it. The drop difference at 100 yards is about 0.8 inches with a 50 yard zero......

 

[18.13]

My bad I thought both were. 25 cal

 

[JimNM]

Think of the pellets as a boat. The wider the pellet the more "wetted" area there is. That is the surface area that interacts with the air. Also consider how heavy the pellet is. A heavy (for it's diameter) pellet will be less affected by the wind than a light pellet.

I shoot .22 in 28.5g and .25 in 25.4 grain. The .22 is less affected by the wind. The .22 is about the same speed as the .25. the .25 drifts considerably more..

 

[Guest]

there seems to be a velocity sweet spot, per ham.

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yup.

 

[harrymoreland]

Thank you for your responses gentlemen (and ladies?).

I am left thinking that out to 80ish yards there's not a lot in it, not enough to drive a desision on what to purchase anyway.

Again thanks



Good luck.

 

[shoot44]

Is there such a thing as a BC for the profile of a pellet?

 

[CurtisNelson]

According to Strelok At 100 yds: the .22 drops 10.7" and drifts 9.6" (lower bc = more drift, higher velocity = less drop)

(20 yd zero) the .25 drops13.3" and drifts 7.0" (higher bc = less drift, lower velocity = more drop)

 

[Centercut]

According to Strelok At 100 yds: the .22 drops 10.7" and drifts 9.6" (lower bc = more drift, higher velocity = less drop)

(20 yd zero) the .25 drops13.3" and drifts 7.0" (higher bc = less drift, lower velocity = more drop)

That’s not what my Strelok shows. What BC are you using for each? Although your assumptions are correct in parenthesis. Why a 20 yard zero? Try 50.

 

[Guest]

Is there such a thing as a BC for the profile of a pellet?

I have personally never seen such a thing. I do not know much about ballistics though, perhaps someone can provide information regarding that? I think the conventional wisdom is that such a "SAC (Sail Area Coefficient)" \(°_o)/ complicates the equation needlessly. That may or may not be true now that we have computing resources in everyone's pocket hundreds of times more powerful than were the computers on the moon lander ...

 

[CurtisNelson]

 

According to Strelok At 100 yds: the .22 drops 10.7" and drifts 9.6" (lower bc = more drift, higher velocity = less drop)

(20 yd zero) the .25 drops13.3" and drifts 7.0" (higher bc = less drift, lower velocity = more drop)

That’s not what my Strelok shows. What BC are you using for each? Although your assumptions are correct in parenthesis. Why a 20 yard zero? Try 50.

20yds is what I use for HFT and I left the settings as is except for the projectiles and velocities since we are interested in the relative differences between the 2 options.

I show a .22 bc of 0.047 on the JSB jumbo monster 25.4 gr

and a .25 bc of 0.062 on the JSB Exact king heavy. 33.9gr

maybe you used the .25 mk2? That is probably the more relevant choice.

Curtis

 

[Guest]

Possibly adjusted it to run with a different drag model?

 

[CurtisNelson]

Possibly adjusted it to run with a different drag model?

I ran mine on the GA drag function.

Curtis

 

[JungleShooter]

I show a .22 bc of 0.047 on the JSB Jumbo Monster 25.4 gr 

and a .25 bc of 0.062 on the JSB Exact King Heavy 33.9gr. 

Curtis

Curtis,

that BC for the .22 Jumbo Monster RD of 0.047 BC seems rather high.... The test data of the comprehensive BC test by HardAir Magazine shows 0.039. 



And a BC of 0.062 BC for the .25 King Heavy seems more like the BC of a slug than of a pellet. The BC tests found 0.046. 


Here're a couple of screenshots from HardAir Magazine's extensive BC tests....  

Matthias

 

[Centercut]

HardAir Magazine tested the .25 Heavy Mk2. Not the King Heavy (Mk1). Not much but different. 
My beef with them is they don’t test at “accurate or normal” pellet speeds. They test the .22 RDM at 718 FPS and the .25 Mk2 Heavy at 654 FPS. What? No one shoots those pellets at those speeds and of course the BC will be low. .

.22 RDMs should be tested between 925 and 975 FPS, and the BC will be about 0.050 to 0.053. 
.25 Heavy Mk2 should be tested at 850 to 900 FPS and the BC will be similar to the RDMs. And the King Heavy Mk1 will be slightly higher. 
It makes a huge difference in BC what muzzle velocity is used. Not sure why HardAir does that with the low speeds? If you look at the JSB BC test charts they test their pellets/slugs at realistic speeds. Their speeds are listed in meters per second.