canting reticle to allow for spin drift

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DenisA
Posts: 1526
Joined: Wed Nov 09, 2011 7:00 pm
Location: Sunshine Coast, QLD

Re: canting reticle to allow for spin drift

#16 Postby DenisA » Mon Feb 19, 2018 8:50 am

Keith I don't have as much experience as you but having been dialling in spin drift for the last 12 months of 6 years shooting, I can say without doubt that the effect of NOT dialling in spin drift can easily be seen in complete direction changes which happens regularly.

The spin drift adjustment can never be perfect but it does compensate for the bulk of a known effect.

Gyro
Posts: 764
Joined: Sat Jun 10, 2017 2:44 pm
Location: New Zealand

Re: canting reticle to allow for spin drift

#17 Postby Gyro » Mon Feb 19, 2018 9:18 am

I'll buy that DenisA. Ive never bothered as I'm still plagued with all kinds of other more basic stuff but I'm willing to try.

I watched Bob Mead talking about spin drift on a youtube video the other day and seems it ain't much ?

So do you have some info on how to work it out for the different bullets ? Regards Rob.

DenisA
Posts: 1526
Joined: Wed Nov 09, 2011 7:00 pm
Location: Sunshine Coast, QLD

Re: canting reticle to allow for spin drift

#18 Postby DenisA » Mon Feb 19, 2018 10:36 am

Seeing as it's not an exact science because of all the other variables, wrongly or rightly, I just trusted my ballistics app after feeding in all the right info. As previously said, after a few shoots I could see I needed to go an extra click over what I have written in the photo.

williada
Posts: 969
Joined: Wed Jul 22, 2009 12:37 am

Re: canting reticle to allow for spin drift

#19 Postby williada » Mon Feb 19, 2018 12:42 pm

Denis, I estimate spin drift and its because I am confident I understand the other variables after nearly 48 years fullbore shooting at long range. You will learn these effects if the basis of your experiments are on good footing. Keep doing it. That starts with a plumb scope and a barrel fitted in the vertical plane of its natural curvature to align with your scope. Spin drift is there and it will vary slightly just as a tune does with altitude density. It is also in the vertical and horizontal plane and influenced by velocity which influences the yaw of repose past the overturning point in the trajectory. This is very relevant to 1000 yard shooting. The RPM is less affected and hardly drops off with distance. Spin drift may be masked with light changes, apparent aiming mark shifts with different mirage density, terrain, trees and wind zones of different strength and direction as well as tune type such as positive compensation. Don't forget mirage is what you see at the target not necessarily representative of the whole course. It can play havoc with your mind as to real zero. Steady wind conditions are a real pleasure to shoot in over 12 mph when mirage has gone. Keith's point is relevant, that at long range the proportion of wind drift is far more significant compared to spindrift. Watch conditions. However, it is on those light days we get done over when masking factors come into play and we ignore spin drift in the calculation yet it becomes a bigger proportion of the allowance.


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