Jeff in Tx,
Well if you've never lived in Alaska in the winter, maybe you can't imagine experiencing windless days. But they aren't all that uncommon up here when a cold high pressure system parks itself over the State. When the wood stove smoke settles in a cloud around the homes burning wood, it's pretty obvious that there isn't enough wind to complicate the observation and measurement of spindrift if it's present in distance greater than the moa groups the rifle is printing.
I agree that spindrift isn't worth trying to predict. I don't agree that it can't be emperically measurably quantified and adjusted for, just like one would adjust for the known effects of crosswind. If a shooter can determine the quantity of spindrift with a rifle/load combination on a dead calm day, then why not correct for that drift on all future shooting days, windless or windy? Once you've quanitified the spindrift do you think if won't be present with that specific rifle/load combination every single time the trigger is pulled?
And if I place three consecutive shots into a 3.6 inch group at 1000 yds and spindrift effectively causes those bullets to move print 6-10 inches right of POA, why wouldn't it be possible to measure and quantify that left to right drift. I'm an engineer too. I'm not saying quantify it down to fractions of an inch, but it's certainly quantifiable within the realm of inches. If I get 9 inches of spindrift at 1000 yds and I'm shooting .36 moa at 1000yds, are you going to contend that because of some engineering training, background, laboratory work, or other principles, it's not possible to quantify the spindrift to within +/- 3 inches? Maybe even +/- 2"? If it can be measured repeatedly, it can be quanitfied emperically with something as simple as a tape measure.
You have some valid concerns. The rifle scope reticle has to be mounted perpendicular to the barreled-receiver and if twisting turrets the scope turrets must track without left to right error. The gun can't be canted left or right, so a bubble level should be employed to minimize canting. Shooter and rifle have to be capable of printing groups at distance that are tighter in diameter than the rightward drift caused by spindrift. But if the bullets dead-on @ 200 yds and if the center of groups at 1000 yds are 9" right on a windless day, and we know that there's a rational scientific explanation for spindrift, why wouldn't you compensate for that spindrift each and every time you took a shot at 1000 yds or other comparable distances.
Dismissing known and quantifiable spindrift effect because you're an engineer? I don't understand what engineering has to do with it.
If you want to state that your philisophic opinion is that spindrift is not worth quantifying and compensating for, well you're certainly entitled to express your thoughts. Trying to convince others that it simply can't be quantified to a fraction of an inch so it shouldn't be quantified at all? That's your choice, but claiming that proces isn't scientific because you're a trained engineer? That's got nothing to do with engineering. It's simply your personal opinion.
When Shawn Carlock tells us he spent a buttload of time shooting and measuring spindrift and he repeatedly observed left to right drift that's consistent with the emperical/scientific body of evidence - how do you conclude that the spindrift he measures can't really be measured?
It may not be worth trying to predict, but if spind drift can be measured and quantified, then explain it can't or shouldn't be compensated for. It's not like trying to estimate a 1 mph wind. If spindrift is present and it's effect is equivalent to a 1 mph crosswind on each and every shot, I choose to compensate for it.
With my own rifles, I may simply sight them dead nuts on at 1000 yds and let the bullets hit left at the intermediate ranges. For purposes of shooting big game sized animals, the mid-range left-word hits shouldn't be great enough to maim or wound. But with no compensation for 8 or 10" spindrift to the right at 1000 yds, a great hit could become a marginal hit. And for those shooting at 1200 -1500 yds, the known spindrift error would be even more significant.
This is a great thread in many ways. It not only describes and provides a ballpark quantification of spindrift, it also IDs the proper way to set up a scope/rifle combination so that if spindrift is observed and measured at distance, then the odds are pretty good that it's not a manifestation of an improperly mounted scope, or a rifle that's been canted clockwise or counterclockwise at the time of ignition.
Thanks to Shawn and several others for sharing their experiences. These guys aren't rookies, and you can pretty much bet they've got their equipment put together plumb with the world. When they say they continue to experience left to right drift at long distance, and what they observe is consistent with the scientifically predictable effects of spindrift, then I choose to believe.
