Spin drift and Coriolis at 1000+

[Broz]

Thanks for the kind words and you are more than welcome.

Lets leave coriolis out of this as it is dependent on the direction of the shot (azmuth) and also involves latitude. Besides I feel its effect is smaller than we could probably detect at only 1000 yards.

So for your right twist 338 with a 300 gr OTM at 1000 yards. 1/2 moa or 5" would be a pretty safe distance to dial left for correction.

Jeff

[Joe King]

Originally Posted by sdowney

Cool. I've heard of shooter. Is Bryan's program available from the google play store for droids?

Scott I would buy Bryan's book Applied Ballistics, his ballistics program comes with it. I think you would find it invaluable.

Products

[sdowney]

How profound.

[Broz]

Originally Posted by Joe King

Bryan's book Applied Ballistics, his ballistics program comes with it.

Products

Is that the mobile app that comes with the book or a PC program? That is a great deal either way.

Jeff

[270 MKV]

Can someone verify the following??

Matrix 165 VLD

MV: 2850 FPS

Barrel Twist: 1-9

Range: 1000 yards


Projected spin drift: 6.38 inches

[submoa]

Doesn't spin drift go up and to the right? And isn't the Coriolis affect the affect of the earth rotation on the POI? hence shooting east POI is lower and west its higher or do I have this backwards?

[LR3]

Submoa, the way I think of it is that if a truck was coming at you or by you from the rising sun what would I do? Or the sun, which is really the effect. Shooting east, the sun is coming at you at high speed and hence bullet fall is less, shooting west it's going away, hence needs to go further, hence drops more. Similarly, shooting north or south the earth will have rotated westward, hence the bullet will be to the right of target shooting north but left if shooting south. At 1000 yds for me shooting north that is aboutb3" and add that to spindrift. At 2000 yds my spindrift is 1.4 moa. So, depends on the direction and where you are how big the effect is but as Broz said, at 1000 yds not huge. I ve tried to setup my scopes with a slight dip to the right so when level it cants to the left (1 minute on a watch face) and except for one rifle I don't seem to have gotten it right and then only at 1000yds. There was a discussion about this about a year ago. Bryans book is excellent in explaining this.