Re: Spin drift
Tiro,
The point I am making is, if you look at the difference between moving my finger from the pad to the joint, "I" lose 1/2" of accuracy at 300 yards... that is just changing 1 variable, the point of my finger. Same rifle, video taped so you can see I am not playing favorites. Its pretty clear to see, 1/2" at 300 would end up being a bit more than SD at 1000 with the same rifle.
That is my point and my sole point, you are welcome to dial for SD for any amount based on any data you like, that is your right and privilege, "I" on the other hand, prefer to use my field data, and what I know to be true "Downrange" based not just off my own experience, but my experience observing an "awful" lot of shooters on the line of varying degrees of experience.
I will say, that prior to the last decade it was not taught and I never heard anyone say, that their wind calls only work from the left and not the right...or the other way around. I would think with 30 years of recorded data from say 1980 when Sniper Schools came into their own, someone would have complained, right or wrong, the wind data doesn't work correctly for both 9 or 3 O' Clock, there would have been a noticeable variance. I will say, and agree 12" is significant, and when we are shooting targets, like a Larue, which is 11.75" wide it would have shown to have been an issue long before someone decided it was important to include.
The Human factor cannot be overlooked, regardless of what the radar says... I will also note, that I invite anyone who uses the SD feature of their ballistic calculator to change the "Zero Range" after having noted the 1000 yard SD variance from a 100 yard zero to something like a 300 or even 600 yards zero. I have found it doesn't change the SD answer, which is highly suspect if you ask me, as that means I can't zero it out.
Now, I don't want to sound augmentative, and I am not being so, however if you read Pesja's Modern Ballistics, he very much under plays it, telling you to get a left hand twist barrel and calling it a day. That it is understood that external forces, like Wind, and The Shooter" are far more important variables, to which I fully agree, as do I agree with Brian. I also would say, each barrels twist and muzzle velocity would play a larger part than taking any radar data, because that is only good for that set up and may not translate correctly to what I am using, so why would I dial in ?
More often than not, we have found if the shooter does their part, many of these factors seem to fall further and further from the surface -- which is why I like the way ExBal addresses it, they recommend you shoot and measure a group around 600 yards and that data is then used -- to me, that is the correct way to address the issue, as I have yet to be influenced to the degree I should be if I were go with the published data on the subject -- to which always seems to include the 173gr bullet which isn't really even used anymore. I will say, years ago, I was personally told it was really only a factor at the transonic point, and not well inside the effective range where the bullet was spinning at a stable rate. That information maybe wrong, and contrary to computer models, but it makes sense to me, and how I look at it. I mean when Pesja tells me it is .002" of an inch at 100 yards, if its compounding all the way to 1000 by what factor brings it from .002" to 12" ?
Question my thinking, disregard my opinion on the subject, but I will say this, I will go 1 shot for 1 shot across the cross with anyone, and have no problem putting my thinking to practical application with anyone. So far my track record is pretty good and hanging out there is not a problem, I'm not scared of being proven wrong, or at least enlightened in a practical manner.