Bullet drop and wind drift

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Steve123

Well-Known Member
Hi all,I would be interested in hearing peoples thoughts on this. All rifles zeroed at 100 yards. I have a .308 and a .17 rem. According to Strelok Pro my .17 Rem when firing a 25g v max bullet at 3950fps drops approx 11.4 inches at 400 yards with a 15.2 inch wind drift with a 10mph side wind. Checking this against a 22/250 firing a 53g v max at a guessed 3700 fps it is no better 15.87 inch drop and 14.5 inch wind drift.

Then the .308 using 110g Barnes bullets at 3100fps 25.77 inch drop and 17.4 wind drift or a 150g set doing 2750 fps( guessed as not tested speed yet) 30.92 drop and 14.6 wind drift.

I keep reading about heavier bigger bullets getting blown about less by wind and how good 22/250's are at 400 yards , yet judging by these figures my tiny .17 Rem is at least as good as the 22/250 with less powder use noise and recoil.

I should point out my main quarry is long range crows/magpies out to 400 yards which are I think difficult to hit at that range.
 
I think your figures are wrong, for the rifles you mentioned above I have got at 400 yards
.17 rem- 17.3" drop, 18.4" wind
22/250- 17.8" drop, 14.9" wind
as you increase the range the .17 will drop off rather quickly. If all you are shooting is out to 400 yards then the .17 is a good option but at the ranges we shoot out to you would seriously be ****ing in the wind with it. Also worth a mention is bullet energy (not with crows but more for the foxes) at 400 yards the .17 has 230ftlbs whereas the .22/250 has 650ftlbs.
 
You're certainly correct when it comes to the hmr against the .22lr. So many people say about the hmr being more prone to wind drift but it is definitely not true. The small fast bullets are in the air for less time and therefore have less time to be affected by the wind.
 
Steve123 said:
.17 Rem - 25g v max - 3950fps - 11.4" Drop -15.2" drift (BC .230)

.22/250 - 53g vmax - 3700 fps - 15.87"drop -14.5" drift. (BC .290)

.308 - 110g Barnes TTSX - 3100fps - 25.77" Drop - 17.4"drift (BC 0.295)
.308 - 150g SST - 2750 fps -30.92" drop 14.6"drift. (BC .415)
Click to expand...

Numbers don't look right
what BCs did you use?

17 - 25gr
ShootersCalculator.com | Ballistic Trajectory Calculator


[TABLE="class: ballistic-chart"]
[TR]
[TD="align: right"]400[/TD]
[TD="align: right"]-17.30[/TD]
[TD="bgcolor: #FBFFF5, align: right"]4.13[/TD]
[TD="align: right"]1.20[/TD]
[TD="align: right"]18.11

[/TD]
[/TR]
[/TABLE]
.224 53gr
ShootersCalculator.com | Ballistic Trajectory Calculator


[TABLE="class: ballistic-chart"]
[TR]
[TD="align: right"]400[/TD]
[TD="align: right"]-17.88[/TD]
[TD="bgcolor: #FBFFF5, align: right"]4.27[/TD]
[TD="align: right"]1.24[/TD]
[TD="align: right"]14.75[/TD]
[/TR]
[/TABLE]
.30 110gr
ShootersCalculator.com | Ballistic Trajectory Calculator


[TABLE="class: ballistic-chart"]
[TR]
[TD="align: right"]400[/TD]
[TD="align: right"]-27.82[/TD]
[TD="bgcolor: #FBFFF5, align: right"]6.64[/TD]
[TD="align: right"]1.93[/TD]
[TD="align: right"]18.45[/TD]
[/TR]
[/TABLE]
.30 150gr

ShootersCalculator.com | Ballistic Trajectory Calculator

[TABLE="class: ballistic-chart"]
[TR]
[TD="align: right"]400[/TD]
[TD="align: right"]-32.35[/TD]
[TD="bgcolor: #FBFFF5, align: right"]7.72[/TD]
[TD="align: right"]2.25[/TD]
[TD="align: right"]14.59

[/TD]
[/TR]
[/TABLE]
 
Both trajectory and wind drift are both directly related to bullet BC and Velocity (time of flight). If a 100 grain bullet with a BC of 0.500 is sent at 3000 fps both it's trajectory and drift will be exactly the same as a 200 grain bullet with the same BC and velocity.

You're always going to struggle with the .17 as high BC bullet availability is difficult. You're also going to struggle with a 308 as the high BC bullets are heavy and the 308 can't propel them fast enough. 6.5mm and 7mm bullets tend to offer the best compromise between high BC, good velocity and acceptable recoil. My 6.5 Lapua with a 129 ABLR running 2900fps and zero'd at 100 yds will drop 25" but drift is only 8.5" at 400 yds. The 280ai running a 150 ABLR at 3150 fps drops 21" and drift 7.5" at the same range.

Drop is easy to dial in. Wind is always difficult to read and is the real enemy, that's what you want to be minimising.
 
NigelM said:
Both trajectory and wind drift are both directly related to bullet BC and Velocity (time of flight). If a 100 grain bullet with a BC of 0.500 is sent at 3000 fps both it's trajectory and drift will be exactly the same as a 200 grain bullet with the same BC and velocity.

You're always going to struggle with the .17 as high BC bullet availability is difficult. You're also going to struggle with a 308 as the high BC bullets are heavy and the 308 can't propel them fast enough. 6.5mm and 7mm bullets tend to offer the best compromise between high BC, good velocity and acceptable recoil. My 6.5 Lapua with a 129 ABLR running 2900fps and zero'd at 100 yds will drop 25" but drift is only 8.5" at 400 yds. The 280ai running a 150 ABLR at 3150 fps drops 21" and drift 7.5" at the same range.

Drop is easy to dial in. Wind is always difficult to read and is the real enemy, that's what you want to be minimising.
Click to expand...

That is very clearly explained thank you. Every day a school day, I had either forgotten, or more likely not understood, that B.C. and velocity trumps calibre or weight variations.

I must go back and edit my misleading earlier comments.

Alan
 
Hi I used .230 for the 25g v max and .290 for the 53g .22 v max, the 110g .308 I used 310 bc which from memory is about right for Barnes bullet head.
 
No worries Alan. A lot of people believe that heavy bullets drift less than light ones, and on average they are right, but it's nothing to do with weight, the heavier ones tend to have better BC's.

There's a really interesting balance also between BC and recoil as you move up the calibres. I have come to the conclusion that for me and my tolerance to recoil the best BC/velocity compromise is at 7mm, with 175 ABLR's at .650 BC and 2900 fps. In terms of drop and drift it matches the 300 Win Mag with a 210 grain bullet but with significantly less recoil and there's little I'm likely to shoot that will need a 210 grain bullet. 142's in the 6.5's are also very good, but it's tough to find a standard cartridge that will launch them much faster than 2750 fps so they don't perform as well as the 7's. That being said a 6.5-06 would do it if you wanted to go custom.

When you go over 30 cal you don't tend to achieve the 7mm ballistics in a hunting weight rifle as recoils become too big to tolerate. You're then into shorter range shooting and how much stopping power you need on your chosen quarry being the primary concern.
 
Frankly it all leaves me scratching my head

I have tried shooting corvids at 3-400m with my .17HMR and I have yet to hit one

I have shot corvids with my 22/250 at similar range and at a guess 75% were hit

Ballistics aside I know which id rather put money on.
 
Just another observation, but once out past 200 to 300 yds, G1 BC values don't hold water very well and won't give you very true-to-life results (IME). If you substitute G7 values, you'll get more accurate results. The Hornady figures for the .17 25gr Vmax are hopelessly optimistic. Real world shooting tests based on actual drop values put the true BC closer to .165 G1, so I wouldn't place too much store in the figures originally calculated.

Look at the comparative form factors and MVs for each.
 
If that is true then a 22/250 will give better chance of hits at 300 to 400 yards. I was trying to justify another rifle.
 
+1 ChesterP.

No matter what the numbers say, you must validate your drops. This is very important. Failure to validate your drops will result in a high percentage of longer range misses.

Chronographs have errors, BCs figures diminish as ranges extend and velocity drops, powder can be temperature sensitive, powder varies from lot to lot, humidity and altitude affect bullet flight, etc etc. Scope calibration if dialling up needs to be carefully checked, lots of good videos on how to do this on YouTube.

I setup boards at 200, 300, 400, 500m and measure my drops and calibrate my Strelock+ accordingly. Make sure you line of sight is flat. Usually the difference between estimated v. actual drops isn’t very much, sometimes its more than it maybe should be (eg for Sierra GameKing 150gr .308 which was my worst). With the calibrated ballistics app subsequent targeting is significantly improved.

So Steve123 thats where I’d start. Check your numbers and then go out to where you shoot corvids and set up some boards and gather some data. Use a good quality anemometer to measure the wind, and a couple of stakes and flappy tape downrange, so you can visually see what a certain wind speed at the shooting position looks like. Once you’ve got a solid dataset (record everything meticulously) you find be able to work out your drops in 10m increments, at which point the corvids will start to worry.
 
dodgyknees said:
+1 ChesterP.

No matter what the numbers say, you must validate your drops. This is very important. Failure to validate your drops will result in a high percentage of longer range misses.

Chronographs have errors, BCs figures diminish as ranges extend and velocity drops, powder can be temperature sensitive, powder varies from lot to lot, humidity and altitude affect bullet flight, etc etc. Scope calibration if dialling up needs to be carefully checked, lots of good videos on how to do this on YouTube.

I setup boards at 200, 300, 400, 500m and measure my drops and calibrate my Strelock+ accordingly. Make sure you line of sight is flat. Usually the difference between estimated v. actual drops isn’t very much, sometimes its more than it maybe should be (eg for Sierra GameKing 150gr .308 which was my worst). With the calibrated ballistics app subsequent targeting is significantly improved.

So Steve123 thats where I’d start. Check your numbers and then go out to where you shoot corvids and set up some boards and gather some data. Use a good quality anemometer to measure the wind, and a couple of stakes and flappy tape downrange, so you can visually see what a certain wind speed at the shooting position looks like. Once you’ve got a solid dataset (record everything meticulously) you find be able to work out your drops in 10m increments, at which point the corvids will start to worry.
Click to expand...

Quite so and with a board at 200 i am struggling to hit the board with a 17 HMR and getting good groups with a 22/250

I was quite excited to get a 17HMR but to be honest I am disappointed.

But seriously a 500m board needs to be 6' X 4'
 
Last edited:
Bullet BC change as the velocity reduces.
As for drop... a cross wind can sometimes cause a bulet to rise.
And, calculated wind drift figures are acedemic, unles you know the wind is constant all the way to the target.
Ken.
 
kenbro said:
Bullet BC change as the velocity reduces.
As for drop... a cross wind can sometimes cause a bulet to rise.
And, calculated wind drift figures are acedemic, unles you know the wind is constant all the way to the target.
Ken.
Click to expand...

Agreed on 1 & 3 Ken, but I would be interested to learn the explanation as to how a bullet rises in a cross wind.
 
ChesterP said:
Just another observation, but once out past 200 to 300 yds, G1 BC values don't hold water very well and won't give you very true-to-life results (IME). If you substitute G7 values, you'll get more accurate results. The Hornady figures for the .17 25gr Vmax are hopelessly optimistic. Real world shooting tests based on actual drop values put the true BC closer to .165 G1, so I wouldn't place too much store in the figures originally calculated.

Look at the comparative form factors and MVs for each.
Click to expand...
It is simple, neither g1 BC or g7 BC are more accurate. They are both based on different shaped projectiles, you simply decide wich out of the g1 or g7 BC bullet profile are closest to the shape of the bullet that you are using. In the case of all of the bullets that the op mentioned the g1 BC will be the most true to life. If he was using a 140gr 6.5 Berger vld then the g7 would be more accurate.
 
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