Norma Diamond Line 6 mm Norma BR 6.8g

Reading these numbers

Both a G1 and a G7 ballistic coefficient are published for this bullet. BallisticApp defaults to G7, because the G7 standard projectile is shaped like a modern boat-tail bullet and holds its coefficient far more steadily across the transonic range than G1 does.

Muzzle energy of 2458 J (1813 ft·lb) is computed from the bullet weight and muzzle velocity above, not quoted from the catalogue. Sectional density 0.254 describes weight per unit of frontal area; divided by the ballistic coefficient it gives the form factor, which is how much drag the shape adds over the standard projectile.

Among the 71 loads of this bore diameter in the database, this one's G7 BC of 0.258 is higher than 20 of them.

Similar 6.17 mm (.243") loads