Q: My mate and I have been using our .25-06 Ruger rifles for varmint-predator shooting loaded with both 87gn and 115gn Nosler Ballistic Silver Tip bullets. To our great surprise we found that we have consistently scored a higher percentage of hits on rabbits at long range with the heavy bullet than the higher-velocity light bullets. I would have thought that having a shorter time of flight, the wind would have had less time to exert an influence on light 87gn bullets. Do you have another explanation for this?
Roland Hall
A: Wind drift is a function of velocity lag, and not directly dependent on the time of flight. For example, the 115gn BST .257 bullet has a sectional density (SD) of .249 and a ballistic coefficient (BC) of .391, while the 85gn BST has an SD of .183 and BC of .329. Calculations reveal that the velocity lag over 300 yards is almost 20 percent for the heavier and 29 percent for the lighter bullet. This means that for a given wind direction and velocity, the 85gn bullet will be drifted 50 percent more than a 115gn one (of the same shape) at this range. The things a shooter has to remember for accurate hold-over to compensate for trajectory are relatively simple compared with the amount of information one would have to memorise to compensate for wind drift with the same degree of accuracy.
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