Bullet drop and wind drift

[ChesterP]

It starts to frazzle the brain Nigel when you also consider that Coriolis effect (more accurately called the Eötvös Effect) also has a horizontal effect as well as a vertical one. For the Northern Hemisphere, at 1000 yards for your bullet and MV etc, that might amount to about 4 inches to the right, and for the Southern Hemisphere, about 4 inches to the left. Unlike the vertical component which needs azimuth of target for the East/West relationship on drop or rise, the horizontal component is left or right only dependant only upon bullet mean velocity and the latitude you're shooting from, so for example, the horizontal components would be zero at the equator and maximum at the poles. for us in the UK, the factor is the Sine of 55.1 degrees (roughly) multiplied by the max deflection value, so your value becomes 4 inches multiplied by 0.82 which is 3.28 inches to the right or 0.31MOA to the right. Whilst not exactly huge differences, when trying for first shot hits on very small targets at long range, you tend to need more than the average shooting app, and need to do the maths so for the odd few people who do this sort of shooting, you may find that they make up their own ranging cards with these things listed for specific loads.

All of this is quite academic for most of us on SD but for those interested, it's worth looking into. I can only speak for myself when I say that the more I learn, the more that I realise I don't know! I'm certainly no expert, just a hobbyist shooter.

 

[NigelM]

It starts to frazzle the brain Nigel when you also consider that Coriolis effect (more accurately called the Eötvös Effect) also has a horizontal effect as well as a vertical one. For the Northern Hemisphere, at 1000 yards for your bullet and MV etc, that might amount to about 4 inches to the right, and for the Southern Hemisphere, about 4 inches to the left. Unlike the vertical component which needs azimuth of target for the East/West relationship on drop or rise, the horizontal component is left or right only dependant only upon bullet mean velocity and the latitude you're shooting from, so for example, the horizontal components would be zero at the equator and maximum at the poles. for us in the UK, the factor is the Sine of 55.1 degrees (roughly) multiplied by the max deflection value, so your value becomes 4 inches multiplied by 0.82 which is 3.28 inches to the right or 0.31MOA to the right. Whilst not exactly huge differences, when trying for first shot hits on very small targets at long range, you tend to need more than the average shooting app, and need to do the maths so for the odd few people who do this sort of shooting, you may find that they make up their own ranging cards with these things listed for specific loads.

All of this is quite academic for most of us on SD but for those interested, it's worth looking into. I can only speak for myself when I day that the more I learn, the more that I realise I don't know!

I was aware of Eotvos and have it included in my drop charts, it was the Aerodynamic Jump I was unaware of.

It's also not really fair that when god made the earth he chose to reverse the Coriolis effect in the southern hemisphere to counteract Spin Drift so our Antipodean friends wouldn't need to think too much about either of them. Not sure Dodgy or John could really get their heads around it anyway

 

[Whitebeard]

Sorry i am using a 17HMR, not a fireball (just to be clear)

Yes i know Chasey and with a advertised velocity of 2650fps (2420fps when chronod) thats why you have failed to hit any!!

Ian.

 

[willowbank]

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'

Elevation and Windage my boy, Elevation and Windage.... Daniel Boon worked it out lol.

Imo HMR is really only good for sniping rabbits out to 100yds on a still mid summers evening.

ATB Willowbank