yep its the buffer, after you suggested that I went and changed the settings from Fine > Normal > Basic and the r10 value increased as the image quality decreased and yes it was set to Fine+Raw
Thanks for that.
There is a Custom Setting Menu item where you can alter the number of shots in continuous mode(in RAW too).
The CSM menu item will be d7m and it's called Max continuous release.
If you set it to (say) 3, then the buffer reading will then indicate r3, if you set it to 9 it will change to r9 .. etc.
If d7 is already set too 100, and the buffer is indicating r10, then this is obviously the upper limit.
D300 shows r17 at 100.