A Question For You Loooonnnggg Range Shooters

[brown dog]

As per earlier post, agree with everyone saying sighters render coriolis irrelevant.

That said, I'm surprised to read that different apps are treating coriolis differently, and that some are believed not to factor in velocity decay. As Pops said, that would be a bit of a pre-school error, but then, apps are written by people who are good at writing apps.

The only benefit I can imagine from turning coriolis off, would be no longer having to input shot latitude and bearing of fire for each shot. So, a reduced data entry requirement.

Anyone got a link to Frank G's thoughts (which, being as they're pals, will probably mirror thinking at Rifles Only)? 

[Ronin]

Post 26 is where Frank adds his view

 

http://forum.snipershide.com/threads/coriolis-effect.155178/

 

 

I see no advantage in not accounting for it with ballistic software at extended ranges 

[brown dog]

12 minutes ago, Ronin said:

Post 26 is where Frank adds his view

 

http://forum.snipershide.com/threads/coriolis-effect.155178/

 

 

I see no advantage in not accounting for it with ballistic software at extended ranges 

Yup. Thanks 😊

In that one he's making the point about latitude and bearing of fire inputs.      ...if they're not updated for every change to bearing of fire or new shooting location, the outputs will be wrong. Sh11t in. Sh11t out.  SISO.

Found another one, where he went a bit flat earth: 

http://forum.snipershide.com/threads/coriolis-effect-shooting-east-and-west.6871954/#js-post-6904777

There's definitely a confusion of effects being talked about, and that's getting meshed with some apps appearing to miss steps.

 

We've all agreed disciplines that allow sighters rather negate the requirement,  I suppose, it's worth saying that if you always shoot on the same range, or in the same valley, at a target on the same compass bearing, the effect will not change from occasion to occasion, and is also rendered irrelevant in those circumstances.

I think it's important to split away SISO (failure to update/input bearing of fire and latitude for each occasion) and any 'badly scienced'  apps that may be around, from the effect itself, which is real and deterministic.   

Properly updated&inputted on a 'properly scienced' app, why would anyone choose to ignore a deterministic part of the error budget?

[Ronin]

Are there any apps that account for lat / long and course of fire bearing?

 

I'm not aware of any that I’ve used over the years having this as a data input from the user

 

it may be that it’s automatically accounts for lat / long but one should be able to input the bearing / path / direction of fire to allow the logarithms to give a true solution 

 

Or am I wrong in that line if thinking (Matt asking you as your probably the most experience ballistician here )

[brown dog]

Andy, thanks, but I think Shuggy may be able to outrun me on this stuff! 😁😊

As to inputs, don't know. I think anything 'Litz' is likely to be 'on' in this respect.  For auto latitude, the thing would need gps. For bearing of fire, either a data entry field or an ability to point the gps (compass) at the tgt and press 'on'.

 

[Avian]

52 minutes ago, Ronin said:

Are there any apps that account for lat / long and course of fire bearing?

 

I'm not aware of any that I’ve used over the years having this as a data input from the user

 

it may be that it’s automatically accounts for lat / long but one should be able to input the bearing / path / direction of fire to allow the logarithms to give a true solution 

 

Or am I wrong in that line if thinking (Matt asking you as your probably the most experience ballistician here )

Field Firing solutions software, http://www.lextalus.com,  uses these as the PDA has built in GPS for you position and you enter range and bearing to target.

[Ronin]

Thanks both 

[Shuggy]

1 hour ago, brown dog said:

Andy, thanks, but I think Shuggy may be able to outrun me on this stuff! 😁😊

As to inputs, don't know. I think anything 'Litz' is likely to be 'on' in this respect.  For auto latitude, the thing would need gps. For bearing of fire, either a data entry field or an ability to point the gps (compass) at the tgt and press 'on'.

 

Matt, you are too kind. I once asked a very experienced ballistic scientist about this and he laughed. Yes, he said, spin drift and Coriolis force are real things, but for Small Arms, they pale into insignificance compared to Ballistic Coefficient, which he called ‘the biggest con job in the history of the shooting sports’. He said that no military application ever used BC, which was a ‘crude approximation’ of true drag. All military applications use true, calculated drag curves, calculated using actual velocity decay, measured with a doppler radar.

[brown dog]

3 hours ago, Shuggy said:

Matt, you are too kind. I once asked a very experienced ballistic scientist about this and he laughed. Yes, he said, spin drift and Coriolis force are real things, but for Small Arms, they pale into insignificance compared to Ballistic Coefficient, which he called ‘the biggest con job in the history of the shooting sports’. He said that no military application ever used BC, which was a ‘crude approximation’ of true drag. All military applications use true, calculated drag curves, calculated using actual velocity decay, measured with a doppler radar.

😂 Lapua offer the doppler drag data in their app.  I think they're the only bullet manufacturer to offer that in the civ market.

I think calling BCs a 'con job' is an odd take. BC are a legacy from the old days and provided manageable best-fit modelling to early (pre-doppler) military ballisticians. They were 'invented' by the military, for the military - intially, almost exclusively artillery.

....things like FACE, AFDC and MFDC used best fit modelling 😉

Subsequently,  significantly, post-war, I would imagine, hobbyists took hold too.

The only conning I could imagine being associated with BCs, would be bullet manufacturers providing 'optimistic' BCs for their products, knowing joe public couldn't readily test them and would buy the apparently 'fastest' bullets.

 

 

....and I'd utterly disagree about drift! (odd that he compared a deterministic lateral displacement quantifiable in metres (in, for example .338 / 8.59 within effective ranges)  to BC fudges?! Wind deflection would have been sequitur) was he also a shooting hobbyist (I suspect so, if he was even aware of BCs) beating a pet hobby horse?!😁

[Avian]

Some ballistic apps, Field Firing Solution, for example allow you to calculate accurate BC for your bullet from observed drop.

[maximus otter]

4 hours ago, Avian said:

Some ballistic apps, Field Firing Solution, for example allow you to calculate accurate BC for your bullet from observed drop.

As does Strelok Pro in a process they call “ truing”.

maximus otter

[Shuggy]

@brown dog What he meant by ‘con job’ was the use of BC as a marketing ploy by the bullet companies, in that you are buying a bullet based on how well it approximates to a ‘standard projectile’ fired by Bashforth across the Woolwich marshes over 100 years ago.

I’m sure that those systems that you mention did indeed use best fit modelling, but aren’t they now considered a bit ‘old school’? 😉

Yes, BC originally had a military origin, but his point was that it is now thoroughly obsolete for modern military applications, now that we have doppler radars. 

Personally, I thought that he was missing the point a bit, as the modern shooter apps are ‘good enough for civilian work’ as they will reliably get you on to the paper at most sensible ranges.

[Popsbengo]

6 hours ago, Avian said:

Some ballistic apps, Field Firing Solution, for example allow you to calculate accurate BC for your bullet from observed drop.

Hornady 4DOF which is free and online.  They even have some doppler decay curves for Lapua pills.

https://www.hornady.com/team-hornady/ballistic-calculators/#!/4dof

[VarmLR]

Out of interest today, I included coriolis in my first shot on target at 600m, and looked at the difference without it being considered.  I'd allowed for an 8mph full wind which seemed to be spot on (it was very consistent most of the day).

For context, first shot on target on a "Macqueens 600m" target was on the outside of the 5 ring, elevation spot on (loads are consistent with lots of chrony data at various temps so confident with those and the BC has been trued by using drop at various distances).  That was with Coriolis added in. The difference without may have been just a few inches at that distance and a little higher, so in that instance with it turned off, I'd have just an inch or so further in and high which would have been closer to the V-bull in that instance.  It's probably not worth worrying about at those distances where trigger technique and wind count for a lot more.   Even if it's been an animal (and I wouldn't shoot one that distance) it would have made no difference to the outcome.

[Moorlander]

Heres a demo

 

[NigelM]

Just some real life numbers.

6.5x47 Lapua, 123 Scenars @ 2940 fps, 29.92 in HG and 50 degF. 0 wind.

Shooting due N or S, Coriolis and Spin drift on in Strelok Pro - 386" up and left 12".

Turn Coriolis off and it's 386" up and 8" left.

Turn Spin Drift off and 386" up and 0" left.

Shooting due E with everything turned on - 382" up and 12"

Coriolis off and 386" up and 8" left.

Spin drift off and 386" up and 0".

Do due W with everything on - 389" up and 12" left.

Coriolis off and back to 386" up and 8" left

Spin drift off and 386" up and 0".

So Coriolis is causing a difference of 7" of vertical and 4" of horizontal depending on what direction you're shooting in.

Spin drift is worth 8" left whatever direction you're shooting in.

Other factors have an even greater effect. Add 1mph of wind and at 1000 meters it's worth 10". Shows the importance of your wind reading. 

My velocity shift due to powder temperature is 2 fps/ degF. go from a 50 degree day to a 70 degree day and it adds 40 fps to velocity. That reduces drop by 19" at 1000 meters.

I have also just invested in a Garmin 701 and have comparing G7 calculations to the Litz Custom Curves. Same set up as above and the Custom Curves give an extra 0.2 mils of elevation over G7 which is 8" at 1000 meters. Explains why I have been having to add a couple of clicks to the Strelok calculations to get centre target at that range and it wasn't the chronograph lying to me as I suspected.

Aerodynamic jump is another factor that has to be considered if there is any wind and can be worth 6" quite easily at that range.

It's bloody complicated if you want to achieve 1st shot hits at that range. Get one small part of the calculations wrong and you can be a long way off target and the odds on blaming the issue on the wrong factor is very high. It's also easily compounded and confused by a rifle that's not shooting inside 1/2 MOA (almost 3" either way) or minor shooter error.

If you have the ability to take sighter shots and can walk it in then much of the above is more complicated than required admittedly.

[Chanonry]

10 hours ago, NigelM said:

Just some real life numbers.

6.5x47 Lapua, 123 Scenars @ 2940 fps, 29.92 in HG and 50 degF. 0 wind.

Shooting due N or S, Coriolis and Spin drift on in Strelok Pro - 386" up and left 12".

Turn Coriolis off and it's 386" up and 8" left.

Turn Spin Drift off and 386" up and 0" left.

Shooting due E with everything turned on - 382" up and 12"

Coriolis off and 386" up and 8" left.

Spin drift off and 386" up and 0".

Do due W with everything on - 389" up and 12" left.

Coriolis off and back to 386" up and 8" left

Spin drift off and 386" up and 0".

So Coriolis is causing a difference of 7" of vertical and 4" of horizontal depending on what direction you're shooting in.

Spin drift is worth 8" left whatever direction you're shooting in.

Other factors have an even greater effect. Add 1mph of wind and at 1000 meters it's worth 10". Shows the importance of your wind reading. 

My velocity shift due to powder temperature is 2 fps/ degF. go from a 50 degree day to a 70 degree day and it adds 40 fps to velocity. That reduces drop by 19" at 1000 meters.

I have also just invested in a Garmin 701 and have comparing G7 calculations to the Litz Custom Curves. Same set up as above and the Custom Curves give an extra 0.2 mils of elevation over G7 which is 8" at 1000 meters. Explains why I have been having to add a couple of clicks to the Strelok calculations to get centre target at that range and it wasn't the chronograph lying to me as I suspected.

Aerodynamic jump is another factor that has to be considered if there is any wind and can be worth 6" quite easily at that range.

It's bloody complicated if you want to achieve 1st shot hits at that range. Get one small part of the calculations wrong and you can be a long way off target and the odds on blaming the issue on the wrong factor is very high. It's also easily compounded and confused by a rifle that's not shooting inside 1/2 MOA (almost 3" either way) or minor shooter error.

If you have the ability to take sighter shots and can walk it in then much of the above is more complicated than required admittedly.

The effects of Coriolis and Spin Drift look an order of magnitude high ? Your data not mine, but a quick look at my 6mm load it seems 2x my values? Odd.

Litz quotes powder sensitivity rates as :

Good Double Base 1 fps/ ºF

Average Single 0.5 ºF

Best Single 0.2 ºF

So part of the answer is you don't run a powder @1000 that you think is 2 fps/ºF ?

[NigelM]

32 minutes ago, Chanonry said:

The effects of Coriolis and Spin Drift look an order of magnitude high ? Your data not mine, but a quick look at my 6mm load it seems 2x my values? Odd.

Litz quotes powder sensitivity rates as :

Good Double Base 1 fps/ ºF

Average Single 0.5 ºF

Best Single 0.2 ºF

So part of the answer is you don't run a powder @1000 that you think is 2 fps/ºF ?

 

That's why it's so complicated. You will not get the same shot solution with a different bullet with a different BC and spin rate in a different place with a different barometric pressure and different ambient temperature with a different wind blowing from a different direction pointing East instead of West. Far too simplistic to say my result is different to yours.

In terms of the powders, quite agree. R15 is a bugger for sensitivity and the new loads are changing over to RS62 which will be less temperature sensitive and a little kinder on the barrel.