Reduced drag from load development
- Thread starter JHard
- Start date
Bryan Litz Ballistics
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I've heard this discussed in the past, only by short range BR shooters.
What's unique about their set up, is that they run twist rates that result in very low stability for the bullets. It's just the bare minimum twist rate to get the bullet to fly mostly point forward.
It's known that low levels of stability compromise BC.
If, during the process of load development, you strike on a combination of bullet and velocity that happens to produce a higher SG than the other combinations, it can have a higher perceived BC, and 'cut' the wind better.
IMO, BR shooters would be better served to run just a little faster twist so they weren't always so close to the ragged edge of stability, to the point where the bullets flight is compromised and it takes load development to find stability when it could be had for simply specifying 1/2" faster twist.
Of course the reason for minimal twist rates is to minimize dispersion due to bullet imbalance and misalignment. This is a way of thinking that goes way back, back to the bad ol' days when bullets had a lot more imbalance than they do now.
The argument is always that precision matters more than BC for short range BR. However, when I see competitive BR groups fired at 100 yards, the decisive measurements is typically horizontal.
My advice would be to spin the bullets just a little faster to get the full potential BC from all available bullets, and don't make instability part of the load development process.
Note, I've never competed in short range BR, so my comments are based on second hand experience here so take that for what it's worth.
-Bryan
What's unique about their set up, is that they run twist rates that result in very low stability for the bullets. It's just the bare minimum twist rate to get the bullet to fly mostly point forward.
It's known that low levels of stability compromise BC.
If, during the process of load development, you strike on a combination of bullet and velocity that happens to produce a higher SG than the other combinations, it can have a higher perceived BC, and 'cut' the wind better.
IMO, BR shooters would be better served to run just a little faster twist so they weren't always so close to the ragged edge of stability, to the point where the bullets flight is compromised and it takes load development to find stability when it could be had for simply specifying 1/2" faster twist.
Of course the reason for minimal twist rates is to minimize dispersion due to bullet imbalance and misalignment. This is a way of thinking that goes way back, back to the bad ol' days when bullets had a lot more imbalance than they do now.
The argument is always that precision matters more than BC for short range BR. However, when I see competitive BR groups fired at 100 yards, the decisive measurements is typically horizontal.
My advice would be to spin the bullets just a little faster to get the full potential BC from all available bullets, and don't make instability part of the load development process.
Note, I've never competed in short range BR, so my comments are based on second hand experience here so take that for what it's worth.
-Bryan
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