POI changes with distance, for a couple of factors, not only gravity and loss of velocity. Bullet path doesn't just vary vertically, but bullets travel in ever-enlarging spirals, due to imperfections in bullet manufacturing, muzzle flip and rotational precession (movement like a spinning top).
You may have attributed it to wind, mirage, etc., but it does occur and is documented by scientific testing.
From the book "The Bullet's Flight" by Mann: Page 243 paragraph 3..."Most bullets, being more or less unbalanced, begin to develop a tip and an oscillation immediately upon their exit from the muzzle, and those that do not tumble in their flight will gyrate, due to air pressure on or near their points."
That's been my experience with 300 win mag development--100 yds is too close to really tell where meaningful nodes are when doing ladder tests.IMHO- As a long range shooter (600 to 1000 yards plus) I will tell you what I have learned. I will never build a load I intend to shoot at long distance by shooting a 100 yards. If I am working up a load it will be at 300 yards minimum. I am not saying it won't work,but I could give you 10 plus loads in a 223 and 20 plus loads in a 308 that will make very small holes at 100 yards, take them out to 600 or more and they fall apart. At 100 yards if a load is going to go South on you, It will not happen that fast. If it works at further distances, then you are good to go, but if it falls apart--Now you have to start all over again. Turns into a lot of wasted powder,bullets and primers. Take the 308 for example,Only because it is so common- You can take one of 8 different powders, 4 or 5 different bullet weights and 3 or so primers. You can zip up a load that will make dime size groups at 100 yards in a heartbeat. What you will find is the majority of them will crash and burn at 300 plus. Again-This is just my humble opinion that I have learned.
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Snyper: Believe whatever you want, but I'm sticking to my comments until there is overwhelming evidence to the contrary. There's more information in the book about the spiraling that I didn't post, and as mentioned, I read the same information in another scientific test.
Mann's pictures in his 1907 book show spiral bullet paths.
I remember seeing pictures from Aberdeen Proving Ground showing artillery projectiles corkscrewing downrange.
As for the reference to Mann's book, the demonstration of a corkscrew flight path, as recorded with yaw cards, was under 1 caliber in radius, and it took deliberate mutiliation to the bullet, and/or deliberate disturbance to the bullets departure at the muzzle (plank shooting).
When Mann set up a shoot thru target to deliberately study group convergence, his result was the same as what I've seen so far: proportional dispersion between two distances.
His conclusion was that bullets do not fly converging paths.
Bryan Litz's modern research shows any "corkscrew" is negligible and rapidly dissipates within a few yards
http://www.longrangehunting.com/articles/epicyclic-swerve-1.php
Each time, the result was the same: linear dispersion at each range. Epicyclic swerve was present, but at a very small magnitude, with a radius less than 0.05”.
This is similar to a claim I've heard here about better accuracy at longer distances that was disproven when actually tested:
On a different forum, a guy set up a 100-600 yard shoot thru for his rifle that typically groups ~2" at 600 yards, but averages 3/4" at 100.
When he set up the shoot thru aiming at 600, he got his typical small group (something like 3") at 600, and, to his surprise, the smallest bug-hole the rifle ever shot at 100!
He was totally expecting to see 3/4" at 100 but the bullets didn't fly that way.
He still hasn't found anyone willing to do his "Shoot-Thru" testing