Targetbuster ,
10 inch is standard and will work well with standard bullets in weights from 55gn to 105 gn .
8 inch required for 105 gn and 107 gn VLD projectiles .
Benchresters shoot 6mm projectiles 70 gn and lighter and use slower twists (around 14 inches I think) in the 6 mm PPC etc.
Standard .243 twist is 10 if you want something else a custom barrel is in order.12 to 14 for light bullets up to 80/85 gr, 8 twist for the 107 vld's for really long range. /ubbthreads/images/graemlins/tongue.gif