Frank Galli weaponised math

[DaveT]

I know that I shouldn't be surprised given the provenance of this concept via Frank Galli but having checked the predictions in his recent book against my own (true) drop tables ... I am just plain gobsmacked by how close they are across multiple calibres!

In my case 260rem and 6mm SLR are either spot-on or max 0.2 mils adrift out to 1000 yards.

I have not checked my 308 or 338 but expect similar results.

I think that I will carry that page in all my gun bags in case I ever lose my hardcopy drop tables or the Kestrel goes bang!

Anyone else done a comparison?

[lapua]

Post a picture of it and i’ll take a look

[brown dog]

It's a bit of a maths parlour trick isn't it? 

Isn't it just postulating a standard trajectory and giving it as a series of step distance changes? 

The parlour trick being variance appears small between the standard trajectory and your round because  you 'reset' the maths at each step distance,

so the discrepancy between the standard traj and your traj doesn't accumulate in a compound way, it keeps being reset to no error and restarting. So the error keeps looking small.

Ie the difference in drop from 300m to 400m ain't that marked In subtension terms, between a 308 and .223  

...so if I say a 308 that's 'on' at 300, needs an extra 0.8mil elevation to get to 400 - and to just apply that same value to the 0.223 ... we find out the .223 was only different over that step distance by about 0.1 mil

If we then shoot the 0.1  error out and put the .223 back 'on' at 400; I could then tell you to apply the 308 change from 400 to 500 for the next step.... and because I've 'reset' the .223, the error will again look small. And so on for each step.

I read some pish that the bloke who 'invented' it has 'doped gravity' ...   pish..    it's a standard trajectory with the cumulative variance of a different trajectory minimised by a reset to zero at each step distance

 

 

 

[brown dog]

So, rather than do any maths, you could achieve the same affect by carrying one random 308ish drop  chart;

putting your 6.5  rifle 'on' at a given range, say 400m, and, to get to 500m, just applying the the elevation delta the 308 chart gives for that 400 to 500 step.... it'll be in the parish +/- 0.2 mil 

[DaveT]

You fried my brain there BD!

All I am saying is that the one sheet would appear to get you damned close on target if your electronics fail or you forget your hardcopy.

[brown dog]

1 hour ago, DaveT said:

You fried my brain there BD!

All I am saying is that the one sheet would appear to get you damned close on target if your electronics fail or you forget your hardcopy.

Sorry - hard to explain well, typing on a phone! 😂😊

Maybe this'll be clearer:

Can the sheet get you 'on' at 600, without shooting every 100m step from 1 to 6?   

Or

Does it tell only tell you the next 100m step after you've shot the one before? 

 

(Ie

Shoot 100 then calculate SWAG for 200

Set 200 SWAG.

Shoot 200, adjust error out of SWAG, record actual setting. 

Do maths on actual setting to calculate SWAG for 300.

Set 300 SWAG.

Shoot 300, adjust error out of SWAG, record actual setting. 

Do maths on actual setting to calculate SWAG for 400.

And so on)

[brown dog]

3 hours ago, brown dog said:

It's a bit of a maths parlour trick isn't it? 

Isn't it just postulating a standard trajectory and giving it as a series of step distance changes? 

The parlour trick being variance appears small between the standard trajectory and your round because  you 'reset' the maths at each step distance,

so the discrepancy between the standard traj and your traj doesn't accumulate in a compound way, it keeps being reset to no error and restarting. So the error keeps looking small.

Ie the difference in drop from 300m to 400m ain't that marked In subtension terms, between a 308 and .223  

...so if I say a 308 that's 'on' at 300, needs an extra 0.8mil elevation to get to 400 - and to just apply that same value to the 0.223 ... we find out the .223 was only different over that step distance by about 0.1 mil

If we then shoot the 0.1  error out and put the .223 back 'on' at 400; I could then tell you to apply the 308 change from 400 to 500 for the next step.... and because I've 'reset' the .223, the error will again look small. And so on for each step.

I read some pish that the bloke who 'invented' it has 'doped gravity' ...   pish..    it's a standard trajectory with the cumulative variance of a different trajectory minimised by a reset to zero at each step distance

 

 

 

All that might make a bit more sense with the sheet instructions!

'Gives a value to gravity' - my arse; it's doing a standard trajectory approximation and taking the error out on each iteration.

[Popsbengo]

48 minutes ago, brown dog said:

All that might make a bit more sense with the sheet instructions!

'Gives a value to gravity' - my arse; it's doing a standard trajectory approximation and taking the error out on each iteration.

Not even worth the effort of rubbishing it,  "gives a value for gravity" indeed.  

[DaveT]

I bow to those with greater experience here but all I am saying is that the table seems to work to get  you on target if you find yourself without drop tables or ballistic calculators.

IE a good backup/ backstop...it seems to me.

[brown dog]

22 minutes ago, DaveT said:

I bow to those with greater experience here but all I am saying is that the table seems to work to get  you on target if you find yourself without drop tables or ballistic calculators.

IE a good backup/ backstop...it seems to me.

Not about experience, Dave, to my eye it's just a sort of trick that's been pseudo-scienced up. 

..I'm still not clear whether you're amazed because you're getting 1 to 1000 having only shot at 100 and 300,

Or whether you're  shooting every distance and correcting to reality on every 100m step before you shoot the next?

 

And I'm also not getting why you don't just write one of your actual drop charts down? 🤔😊😊

[DaveT]

BD...  I already shoot successfully well beyond 1000 and have my trued hardcopy drop tables as well as AB on a Kestrel 5700 so I am completely sorted across my various calibres.

The minor point that I was trying to make is that if I was to be asked for drops for an unknown rifle and given only an initial true drop at say 300 yards then the Galli table (regardless of whether its voodoo or math) appears to provide a fairly accurate starting point vs having to put every variable into a ballistic calculator.

I was shooting at Bisley earlier in the year next to a bloke that only had a short range drop on his 308......  he wasn't getting anywhere near on target!

He also had no ballistic calculator to hand so what he was thinking in jumping straight to 1000 yards on a wing and a prayer is an open question!

To be honest I wasn't in the mood to drop everything  that I was doing and setup all his data in AB  but the Galli table might have provided enough to get him on target safely.

Absent of either he was firing blind and the RCO quite rightly told him to sling his hook!😀

I don't need the Galli table but as I said......  its better than nothing on the face of it.

[brown dog]

... but equally, you could have told him to apply the same come up for his 308 as for your 308 or 6.5 tables, because it will be 'in the parish'   - that's all this 'gravity dope' table is doing.

[brown dog]

Idle moment,  and this has caught my interest, without the 'reset' at each 100m step before shooting the next, this eg would be missing by 1.4metres at 1000m

(This example does the 'weaponised math' extrapolation from a 100m zero coupled with a  300m data point ... with no resets as each distance is shot in turn - it's the resets at each distance that give the system the illusion of being accurate)

[DaveT]

Well down the rabbit hole now!😁😀😀

 

[brown dog]

51 minutes ago, DaveT said:

Well down the rabbit hole now!😁😀😀

 

😂

[Popsbengo]

Funny how a simple 'rule of thumb' method takes on voodoo status.  

There are clearly the occasional true expert - Bryan Litz for one,  however I think many 'systems' advocated in and by the shooting community are at best approximations  - many are mathematically unsound, especially the use of statistical data.

I give you an example:  quoting standard deviation on a sample of three 🤨

[SMLE]

31 minutes ago, Popsbengo said:

I give you an example:  quoting standard deviation on a sample of three

👏

[Ronin]

19 hours ago, DaveT said:

Well down the rabbit hole now!😁😀😀

 

 

 

Agrred but BD correct that The weaponised system only “works” incrementally

Huge step  up in distance means error factor increased 

 

easier with drop table hard copy in writing 

 

 

 

 

[DaveT]

👍I have my verified drop tables. 

Just looked like a magic bullet (as if) for anyone stuck in the field without verified drops.