How do they forge turbo 617 pistons?

[rorax]

There seems to be little info on the manufacturing process involved in forging pistons for the om617, namely the turbo model.

There's a cavity in the crown for an oil duct, but what I want to know is how in the name of Rudolf this is possible... I could see how it could be done with a casting, but how is this accomplished through a forged piston? Beats me...

Also, if any members have some pistons that are unusable anymore, consider donating one to me so I could cut it open for the sake of curiosity and boredom... If I do I'll make a thread, seems somewhat interesting.