The way you do this is interview elsewhere, get an offer for 40% more, and _then_ tell your manager that you have an offer for 40% more and that you'd really like to stay but they'd really have to do something about compensation. You'll get more than 5% then (but likely less than 40%). It's annoying that you have to invest the time for this, but it does provide data to your current company that your market rate is in fact what you think it is.