Dwell readings changing?

After replacing the points, getting it in the ballpark with the feeler gauge, then checking with my dwell meter, I'm puzzled by readings that vary wildly. Looking for 30-34, but I'll see a 5, then it'll jump to 20, then 24, then 40. What gives?

I was able to set my timing and the engine is running okay. Bad dwell meter? Or is this a sign my distributor is worn? Time to switch to electronic ignition?