Ok, it's a mad idea carving miniatures so small, but I try and the result is not so bad. Special thanks to GW plastic, very soft.
If Imperial Guards are 6 mm tall, Space Marines must be 7 mm tall I think.
Then I changing measure: 5mm for Imperial Guard and 6 mm for Space Marine. Look at the comparison. Chainsword of the Sergeant is a nightmare to carve...
New Space Marine, with a more dynamic pose.