Measuring motor current (anyone tried this?)

[DonRotolo]

I have a need to measure the current draw under load of each of our four CIM motors, to diagnose which of the four is drawing more than it should. (This isn't meant as a long-term measurement, more of a quick diagnostic)

Looking at the 40A snap-action fuse, I see the copper connection feet pass all the way through the body and have a small part that comes up through the top of the breaker.

My thought is to measure the voltage drop across the breaker, and use that to calculate the current draw. My multimeter cannot measure above 10 Amps directly, under load the motor draws more than that.

Has anyone ever done this? Is the voltage drop reasonably measurable? Can I measure to within 1/2 Amp this way?