"However RAW images are normally 300dpi so I suspect that a convertion your doing somewhere is changing this to 240dpi. I remember this happening to me when converting to DNG when transferring off camera. A quick play in the convert settings fixing it."
No. Out of camera they are normally 72 PPI. when converting from Raw you have the option to select what PPI you want. Once selected, all converted images will reflect the setting you selected. See attached photo. Just alter the setting in the workflow options box.
Access Workflow Options by left clicking on the text bottom centre of the Camera Raw page.
Just a small point, DPI is a printing term, what you actually mean is PPI. (Pixels Per Inch)
Harry