Originally Posted by spittinfire
I understand that. I should have been more clear. How does rate of twist affect accuracy with various bullet weights?
All bullets have a natural center of axis, yes? In order to get the bullet spinning on that axis it is necessary to propel them in a controlled way, in the barrel, so that they don't wobble or go end over end.
A light bullet, spun too fast, can over rotate and come part. A heavier bullet not spun fast enough to generate rotation on it's own axis will result in the wobbling effect.
The ideal medium is to find at what twist rate, and for how long in the barrel, will it take for a bullet to achieve it's optimum rotational ability without spinning it apart.
I imagine there are physics and other factors involved, but essentially you are trying to achieve the optimal spin in the barrel that will keep the round spinning on it's own axis to achieve maximum accuracy.
This is where "Spin Drift" comes in. Some bullets that are spun correctly, like a .308 round at 500 yards, will have a negative effect from that same speed of rotation the longer it is in flight. At 1,000 yards or further a .308 round will experience Spin Drift where the round itself is generating enough motion to negatively affect it's accuracy.
Once again, it's all a balancing act. Spin it too fast, you lose accuracy, don't spin it enough, you lose accuracy, spin it correct at one distance and lose accuracy at a much further distance.
That is why long range shooting is one of the hardest things to do. There are so many variables that it's mind boggling.