500--

Unknown. The 338 Lapua was developed by the Fins exclusively as a long range sniper round due to deficiencies
of the 308/300WM and the logistical problems of the 50.
It was based on a beltless version of the 416 Rigby and not from any version of the Jeffery. Its goal was an accurate 250+grain bullet at high velocity to whack 'em at up to 3000 fps.They accomplished that.To my knowledge there is no relationship between them.

The accuracy of the 338 Lapua comes from the same principle as the 308.,a wider shorter column of powder to burn.It only makes a practical difference past a quarter of a mile, but if you are a sniper shooting a boattail bullet, thats signifigant.