To be clear, I have a little device that I don't know what it's called, that I can drop the bullets in to check fit. It's just a piece of aluminum with an imitation chamber in it and I look for the case end to set flush. So when it "reshapes" the bullet, it's just squeezing it to a slightly smaller diameter.
Camera phone pic isn't the best. There's a little ridge in the lead that you can see. I think it forms during seating and occasionally catches before the case edge. Just pushing it into that tester with my thumb clears it up, but I'm guessing more bell is the correct answer.
