not that bad tho only a tiny hard type noise but silent once hot id say if it rattles that bad ur bores have been bored slightly to big or are very worn and the noise u get is known as piston slap not forged pistons !
i did say when cold, and the bore clearance is also dependent on application, on both forged engines i have owned the pistob slap although quiter when warm hadnt completely dissapeared.
I know that wossner and wiseco pistons each have different bore to piston clearances depending on the level of tune the engine is supposedly gonna be built to,
i know when i had the engine machined the engineer asked me what it was going to be used for and i said track days and high boost 24psi, and i had the intention of changing the turbo at a later date and running 2bar possibly so the enginner chose the larger of the clearances,
going for this larger clearance meant that the engine was consistently rattly, although it was quieter when hot it wasnt exactly silent, now because of this larger clearance being used the engine was never gonna last forever as effectively it was a race engine and therefore should have regular strip downs and refreshs,
basicly you cant say that the engine has been overbored just cos its a bit rattly if you dont know what its been built to.