From experience I would recommend the Mec 600 jr. I still have a couple Lee 410 loaders but they don't work worth a hoot with the new hulls and thats any brand of hull.
About 15 years ago I aquired an old Mec jr in 410 with a set of 20ga dies, and assorted bars & bushings (the guy gave it to me). Being busy it just sat in the shop for years. A few years ago I went to load some 410 rounds with the Lee loader and found out with the newer hulls it just wasn't going to happen.
I dug out the mec and set it up with bar and bushing for the load I wanted. Immediately I started experiencing shot bridging in the shot drop tube. The darn thing would drop the shot when I let the handle all the way back up and I had shot all over the floor.
I unscrewed the tube and upon looking at the inside you could see the roughness from manufacturing. I took it to work and cut a length of rod split the end for emery paper, I put it in an air drill and started polishing with one of our oils as lube. Use gloves as the tube will get hot quick when the air drill hits max rpm. Ask me how I know that. I used progressively fine paper finishing with crocus. I then finished the job with cloth and wax leaving the inside snooth and very highly polised.
Now with the old Mec I get full length sizing on every case, no shot bridging, and perfect crimps on every round.
Sometimes when wife wants to go for a ride we drive by a public range where I hit the garabage cans. I have found up to 300 empty 410 hulls on a good day.
Find an old mec, you will be much happier.
