Hi Blackhand, thanks for the warning. AeroShell 500 is the manufacturers recommended oil for the GTD-350, so it should be entirely suitable with any luck.
For the Williams WR27-1 the Navy only specified that the oil must meet MIL-PRF-23699 which both AeroShell 500 and BPTO 2380 do, so again hopefully everything should be ok.
It would be nice if I knew what the actual oil the Navy used in the WR27-1 was and could get hold of that I agree. All I know is that the original oil smelt like a farmyard and gave me a cracking headache.