Re: Spin Drift at 1500 yards
If the shooter can't execute the firing task properly, then most anything we correct for has little meaning. The solution is not to ignore the corrections, but fix the shooter.
If there is a 2 Mil variation in holds with the same rifles and ammo, some shooters need an adjustment. Even if it gets a hit, it's still wrong and needs to be addressed.
In some prior threads we all agreed that mechanical zero is zero, it does not change for other shooters. If it does, there is a shooter problem, and the real fix is not to reset the knobs on the scope.
Seriously, if I get assigned to someone as a spotter, and he tells me "I yank about 1.5 MOA right, so you'll want to adjust your wind calls for that", should I suggest he get a left twist barrel to even that out?
The physics of the shot are just that, it's math, and there is AN answer, not an answer that works for you. If you can't apply the fundamentals and get the answer to work, it's not the math that's flawed.
Factoring in the shooter just means we account for the percentage of time the shooter fails to execute properly. If the rifle/ammo combo produces 1/2 MOA groups at a given range, then a 100% shooter would hit a 1 MOA target 100% of the time, presuming all variables like wind were properly accounted for in the solution. If the shooter only executes 50% of the, then under the best of conditions you can only expect a 50% hit rate. The solution is still correct. Certain variables, like wind, cannot be precisely measured, so there is some error there, along with potential range and angle errors. We cannot know the actual velocity for a given shot, nor the actual drag of the bullet. The solution forms the CEP, circular error probable. Our job as a shooter is to center that CEP on the target each and every time. The more often you do that, the more often you hit. If you ignore spin drift, you are moving the CEP away from center, therefore reducing your hit probability. How much depends on the size of the CEP, the target size and the amount of drift.
Try this. At 2000 yards, 1 MOA is 20.94". Make a 21" circle from a piece of cardboard. Now center that on an IPSC target, 18"x24" in the body. If you are perfect, there is still a percentage chance you miss, since the bullet can land anywhere in that circle and some of the circle is not on the target. At 2000 yards, spin and CE for a 250gr Scenar at 2970fps is about 41", depending on latitude, etc. Move the center of the circle 41" to the right. How much is on the target now? 1 mph of wind is about 17" of drift, so spin and CE are about 2.4 times more in value that a 1 mph wind value. Even if you are a perfect shot and make a perfect wind call, what's the percentage chance of making the shot. If you put in the SD and CE, a 1 MPH error still leaves some chance of a hit. If not, you need to make a 2.5 mph error in the wind call, TO THE LEFT, or you have about 0% chance.
This is what I mean about lack of correction screwing with your wind calls. You need to see the exact same downrange indcators with a 2.5 mph differance if it's L-R or R-L. It's hard enough to see what the wind is doing, you really want to make it MORE complicated?
Now, if you keep yanking the trigger, or have a chronic flinch, PIP, or other shooter error, please ignore all this right now and get to a class and get it fixed, because until that's done, this does not matter.
