BC Consistency
01:19:47 |
Bryan and Francis cover Chapter 5 of the new book: Modern Advancements in Long Range Shooting – Volume 3 which is BC consistency. This includes a discussion of shot-to-shot BC variation of conventional and solid bullets as measured by Doppler Radar. The consequences of BC variation are discussed in the context of both PRS and ELR applications. We also talk about methods of uniformity and sorting for BC.
In the PRS data, there are cases of wide BC SDs distributions within the same bullet (brand and weight). Is this an indication of worn out barrels? The talk alludes to the symptoms showing up at long range. Given that the average shooter won’t have the ability to measure BC what early early indicators can be used to predict when BC SD will start to impact down range performance? Interesting side note that ‘shot out’ barrels will continue to shoot reasonable groups at short range. Keep them for practice I guess…
Good question Rob! The wide variations of BC SD for a specific bullet are likely to be caused by a mix of bullet lot-to-lot variation (mostly likely), barrel wear state (likely), and/or ammo handling characteristics (least likely, but plausible). It is true that barrels will tend to have slightly higher (worse) BC SD as the round count increases. Unfortunately, there aren’t any “early” indicators for barrel BC SD migration; by the time you see large vertical groups at extended ranges, either your muzzle velocity has gone erratic and/or your BC SD has shot up dramatically. The only way to verify a BC SD issue is with long range radar tracks.