It’s natural to think that Ballistic Coefficient (BC) variation must come from differences in bullet geometry, and that’s one source of it. The shape of a bullet will affect its aerodynamic force, and even small variances will have great effects on the aerodynamic drag. This is why some competition shooters sort bullets, trim or point the tips of Open Tip Match (OTM) style bullets, and other practices to achieve uniformity.
Selecting and forming bullets for uniformity can improve your shot-to-shot BC variation if geometric variations are the primary cause of BC variation. However there are other sources of variation as well. Even if your bullets are all the exact same geometry, it’s still possible they will suffer from shot-to-shot BC variation thru other mechanisms. One way this can happen is lack of dynamic stability, which is often a problem at transonic speed (below about 1340 fps), but can be a problem in supersonic (right out of the muzzle) as well.
High BC variations that are stability related tend to be found in one of the following cases:
- Solid copper bullets that are longer than lead core bullets of the same weight are so less stable from the same twist.
- Lead core bullets that are exceptionally long for their caliber can be difficult to stabilize as well. Such a bullet can be perfectly stable at the muzzle, but become erratic at longer range.
We cover this a little bit more in our following article, How Stability Affects BC Consistency.
Berger bullets are designed for long range shooting in mind and developed with live fire doppler radar testing, which measures the consistency of shot-to-shot BC variation to guarantee your groups will stay together at distance. There are occasionally bullets with higher BC’s than Berger, but in most of those cases, that high average BC is very inconsistent due to overshooting the length/weight that can be consistent in that class. In other words, Berger bullets are built to have the highest performance that is possible while maintaining shot-to-shot consistency in BC.
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What is a BC?
BC, Accuracy, and Precision
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