The only thing you've brought to this is pulling five grains out on a hot summers day....

For my criteria the trajectories do match.The trajectory of the hunting bullet is the only one that needs to be spot on, the rest is just for practice/play. Ican live with a little difference on steel plates and milk jugs....which I don't start to see until you cross the 3 or 400 yard line anyway.If my hunting bullet is 1/2 MOA andmy play bullet is 3/4 or 1 MOA, I really couldn't give a rats azz.

Say you run aload test at300 yardsand 37.8 grains of powder is the published maximum.

Out of that test you pull 37.0 grains as your "OCW load".

36.6 grains and 37.4 grains both shot into the exactsame pointof impact and all three charge weights averaged 1.6 inches. IN OTHER WORDS, if you shot 3 rounds of each charge weight, 36.6, 37.0, 37.4,they would all fall into the same 1.6 inch group. 36.2 grains and 37.8 grains are bothvery, very close to the same point of impact and are still yielding a 1.6ish inch group.By picking the middle of the sweetspot, 37.0 grains, you have just found a load that is damned near 1/2 MOA and isvery tolerant of pressure changes both UP and DOWN. (Tweaking seating depth will likely tighten up that 1.6" group.)

Because those three to five different charge weights show on the target that they impact the same place, you can know that the shock wave from theinitial chargedetonationwhich slings back and forth from chamber to muzzle ("barrel harmonics") is at it's furthest point from the muzzle, causing the muzzle to be at it's calmest period of movement. This occursin at least two places in a work up.You want the bullet to exit at that instant to reduce or eliminate anybarrel whip influence on the bullets flight. The tolerance to pressure differences and the reduced barrel whip are proven by thetest you just shot.

Those pressure differences can be influenced on a load from several avenues....

Differences in charge weight caused by volume measured charges.
Differences in case capacity cased by lesser quality brass.
Differences in some case prep.
Differences in bore condition, fouled vs. recently "clean".
Differences in lot # of powders or primers.
Differences in temperature or humidity.

By picking the MIDDLE of the sweet spot (Optimal Charge Weight), and precisely weighing out your37.0 grain charges, you've just allowed the load to be less sensitive to any of those variables and proved it to yourself by the test you shot above because you have a range of pressure differences both up and down that shot into the same group. You could run with 37.8 grains but you do not have the luxury of pressure tolerance on the UP side, which is why you have to pull 5 grains out on a hot summers day.

The side benifits of having the bullet exit at that point in time when the muzzle is at it's calmest are...

Similar bullets of same weightcan be made to shoot to very close trajectories, allowing swap loads.
Skinny barrels can be made to shoot just as good as fat barrels if heat issues are paid attention to.
Some mechanical issues become less of an issue, floated barrels vs. pressure points, ect.
Ugly stuff like the BOSS and that SIMMS rubber thingyare not needed.

If this didn't explain it then just go read the Newberry'slink as many times as it takes to sink in. It ain't rocket science............