There's a wiper in the Lee PPM that can wear down after a lot of use--especially if you use a lot of "scratchy" ball type powders.
You can replace this wiper--or do what I did and cut a shim from some clam shell packaging (thin piece of plastic) and put under the wiper... and it's good as new again.
Polish the interior of the drum with 400 grit sandpaper if it gets rough after several thousand rounds. I thought I had worn my PPM out, and ordered a new one from Midway (for 25 dollars), and while I was waiting for it to come in, I went on and polished the inside of my old one, and shimmed the wiper... and W748 meters smooth as silk once again--with no leaks.
Practical Long Range Rifle Courses...
Optimal Charge Weight handload consulting