I think System246 discs are basically the same as normal PS2 DVD's?, so you should dump it like any other DVD (using isobuster or dvd decrypter for instance).. the format will be 2048 bytes/sector .iso.
RAW dumping (2064 bytes/sector) is possible if you have an LG drive which can dump gamecube/wii discs, but I don't think it's of any use for most DVD's. And you won't be able to burn these images, because there are no drives which support RAW DVD burning, so it's basically pointless.
@Vigi- funny that. just purchased a GDR-8162B. day late, dollar short, & all that jazz. will test this against PlayStation 2 DVD-ROMs when i get around to purchasing the few that were ports of SYSTEM246/256.