Frequently, observations - regarding precision rifle shooting/reloading - are proffered in terms of absolute value: in benchrest shooting/competition, there is but one absolute: NOTHING is ABSOLUTE . . . following a tangent, or two, we’ll come back to this . . .
 
As more information has become available (shared) regarding the technical aspects of precision, a growing number of shooters handicap their potential by becoming focused on [technical] attributes, many of which are, “lost-in-the-noise”. A surprising number of individuals, locked into the technicalities, never consider how even a minimal ‘wind’ (condition) may affect shot placement on the target - or, enlarge the group. Largely, ‘wind’ remains either misunderstood, or, at best, underestimated.

The principal misunderstanding: the penchant for comparing wind-drift (say for two bullets of the same caliber, but with differing ballistic coefficients -BC) via a relatively large [wind] velocity component (5,or,10 MPH), as opposed to a lesser velocity - say plus/minus 1MPH - a component more reflective of who, on a given day, will win/place/show. A 5MPH mistake is one from which recovery is unlikely.

At a target distance of 200 yards, assuming the mythical/hypothetical and constant 10 MPH wind, at the even more unlikely steady 90 degree vector (angle), the average benchrest quality bullet (from 68 Gr. 6mm through 120 Gr. .30 Cal), will be dragged about 4.1 inches! This is a number which, often, startles even the most experienced benchrest competitors!

Wind-drift is directly proportional to [wind] velocity, therefore, it is easy to visualize a mere 1 MPH change in velocity - while assuming a constant angle - moving bullet impact 0.41” at two hundred yards. Assuming a rifle capable of shooting a perfectly concentric, or, ZERO (0.000”) center-to-center group EVERY time, a two mile-per-hour shooting window results in a full 0.8” of left-to right (horizontal) group size . . . who can ‘dope’ that window? (Note: we won’t even open the discussion to gyroscopic laws, which, being a gyro, the bullet MUST obey. These laws, dictate varying degrees of “vertical” in association with the forces (drag & RPM) applied. Since we either shoot at ROUND (bulls-eye) targets [for score], or, for group, measure the extreme spread, the hypotenuse becomes all important!)

At 100 yards, exposed to the same mythical condition, bullet drift is a mere 1/4th of the 200 yard figure: the 200 yard game, thus, requires a much higher level of wind/condition doping skill: the target size is proportional to distance (doubled), but the cost of a ‘doping’ error is four times greater.

An amazingly high percentage of individuals, with whom I speak, expect to be able to, CONSISTENTLY, shoot sub 0.40” groups at 200yards! This level of precision requires a maximum of 0.20” (0.10 MOA) precision, combined with the ability to ‘read’ conditions (wind) to [within] +/- 1/2 MPH; or, during varying angles, the perpendicular/velocity equivalent, within plus or, minimum 0.50 MPH - who is consistently capable of doing THAT?

Back to the beginning. There is no such thing as absolute velocity - to the degree many believe, the chronographs we use will not precisely measure velocity. Bullets [from the same box/lot] do not share a common (absolute) BC, but, rather, vary: often, considerably! A Doppler RADAR test, conducted at White Sands, NM, of which I am aware, showed a BC range of up to 15% - that, by the way, for VLD type bullets - stuff to think about!

While, using a decent micrometer, we may measure case neck-wall thickness, bullet diameter, etc., to the one-ten-thousandth (0.0001) of an inch - even that producing a merely relative result : one man’s .3080 may be the next man’s .3079, or, 3081 - not particularly absolute - only close. Mother Nature works in degrees of variation. At 200 Yd., a 2MPH wind reading error results in 0.80” of wind-drift - when it come to winnning/losing, that is, “where it’s at.”

So, what’s the point? Initiates should read a little, master the fundamentals, and shoot a LOT - and IN CONDITIONS - not the wee hours of the dawning. [The late] Don Judd, upon delivering my first “real” benchrest rifle - a .222 &1/2 - advised that, “after a couple of barrels, you might begin to “catch-on”! The only absolute: some things never change . . . oh, one more cliche, “don’t sweat the small stuff” . . . RG