Originally Posted by
MistWolf
Once I took a frog and placed it on a bench and said "Jump frog, jump!" The frog jump. I then cut off a leg and repeated the experiment. It jumped, though not as well. I did the same with two legs removed then three. Both times the frog at least tried to jump. Then I cut off the fourth leg. When the frog was given the order to jump it did not. My conclusion: Without legs, a frog cannot hear.
I use this story to illustrate the point the right observation doesn't always lead to the right conclusions. Mass is not the only factor when calculating a bullet's ability to buck the wind. The 200 grain 30 caliber bullet being used for long range shooting is a long skinny spitzer with a good BC. If you use 30 caliber 200 grain roundnose with a dramatically lower BC, not only will that bullet get pushed around by the wind more, but it will shed velocity faster.
The reason the 5.56 displaced the 308 as the preferred caliber for the 600 yard service rifle matches is because they found the longer 22 caliber bullets have a better BC than the 30 caliber bullets, shoot flatter, buck the wind better and do so with less recoil.
6.5mm bullets have always been long for the caliber and have good BCs. Though launched at slower speeds, their BCs allow them to retain velocity and buck the wind better than 30 caliber bullets launched at higher velocities, and the 6.5s will stay supersonic for a longer distance although they have less mass.
Time of flight plays a large role in resisting wind deflection. A bullet launched at a higher velocity is in the air less time, giving the wind less time to push it around. So if you launch two bullets of the same BC, the one with the higher velocity will have less wind deflection over the same distance.
While mass helps, it's not the whole story, nor is it the most important part. A lighter bullet with a higher BC will fly flatter and buck the wind better than a bullet of greater mass and a lower BC.
It doesn't mean the 30 caliber is a poor choice. It carries more energy. In the case of the 300 magnums launching 200 grain bullets, that energy will be felt at both ends as it will take it's toll in the form of increased recoil