I believe around .043. I've read velocities from high 700's to high 900's with great accuracy. My wildcat shoots them at 815fps. There awesome. The only pellets I've used lately. Just ordered another dozen tins. Mk2's
I am using 0.054 as my BC on the heavies. Mine shoots the pellets Out at about 828 fps. With this BC the gun is accurate from 80 yards to 160 yards. Also when I feed this data into Sterlok, the readings are accurate at multiple ranges.