The data! 338 Lapua Improved. 32" barrel. 104 grains Retumbo. 300 grain Berger bullet. Cases have been fired several times. The velocity spread was around 10 fps. Unfortunately, accuracy wasn't that great. Mirage was horrible, it's been well into the 90's. At 425 yards, I shot several groups, I would have two almost touching and others a bit away. I'll attribute this to mirage, the bull was dancing around quite a lot.