I expected group size to be proportional to range, at least to 200 yards or so. I was wrong.
Group sizes at 200 yards are greater than 2 times 100-yard group sizes. For the 506 CBA National Match records from 2000-2013, 5 shot groups at 200 yards are 2.236 times the size of 5 shot groups at 100 yards. The ratio for 10 shot groups is 2.385.
Group size MOA increases as range increases, at least in those CBA matches.
Taking that, I assumed that “conditions” caused the increase, and worked out an elaborate and riviting analysis of the effect of wind and shooter compensation for wind.
Then “husker” presents data at 50 and 100 meters for 10 shot group size shot in a tunnel.
This, husker's, data, if representative of a larger sample, means that my wind analysis is wrong. I'm wrong again.
(Assume constant bullet forward speed.) If group size, in MOA, increases with range, then either something extraneous must happen to the bullet, or a speed caused by an acceleration = vector must be imposed upon the bullet between muzzle and closest target.
Wind is an extraneous force that operates on the bullet between, say, 100 and 200 yards. A 1” 100 yard group would turn into a > 2” 200 yard group if the wind continued between 100 and 200 yards. If there were no wind between 100 and 200, and no other effect, the 1” would become 2".
A speed caused by an acceleration = a vector, is imposed on the bullet by the wind between 100 and 200 yards. If the bullet is moved 1” in 100 yards, that speed-call it a sideways movement for example, is 1” per hundred yards. That sideways speed will continue from 100 to 200 yards.
First, group size doubles as range doubles, a 1” group becomes 2". But, since the wind has put a sideways speed on the bullet of 1” per hundred yards, the group becomes 3" And, since the wind is still blowing on the bullet, another inch makes 4” groups. So, wind drift varies as the square of distance, and that's about what wind drift calculators show.
BUT
Group size increases with distance and NO WIND, as husker's data shows. Something's happening, and I don't know what it is.
We need either an extraneous force on the bullet from D1 to D2, or the bullet to be moved sideways, to accelerate.
Mann's explanation of x and y on page 256 doesn't show either.
I find the introduction of data to be most upsetting to my preconceived notions.